Radio frequency transceiver front end circuit with direct current bias switch

ABSTRACT

A front end circuit for coupling an antenna to a radio frequency (RF) transceiver for time domain duplex systems is disclosed. The front end circuit includes an antenna port, a power amplifier, a low noise amplifier, and a matching network. The output of the power amplifier and the input of the low noise amplifier are coupled to the matching network and connected in common to the antenna. The power amplifier and the low noise amplifier are activated and deactivated in sequence corresponding to the transmit and receive modes of the transceiver, and the matching network minimizes the effect that one has on the other at the designated operating frequency.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.12/412,226 filed Mar. 26, 2009, which relates to and claims the benefitof U.S. Provisional Application No. 61/150,419 filed Feb. 6, 2009 andentitled SINGLE-BAND TRANSMIT-RECEIVE FRONT-END INTEGRATED CIRCUITS FORTIME-DOMAIN DUPLEX APPLICATIONS, which are wholly incorporated byreference herein.

STATEMENT RE: FEDERALLY SPONSORED RESEARCH/DEVELOPMENT

Not Applicable

BACKGROUND

1. Technical Field

The present invention relates generally to radio frequency (RF) signalcircuitry, and more particularly, to single band transmit-receivefront-end integrated circuits for time domain duplex communications.

2. Related Art

Wireless communications systems find application in numerous contextsinvolving information transfer over long and short distances alike, andthere exists a wide range of modalities suited to meet the particularneeds of each. These systems include cellular telephones and two-wayradios for distant voice communications, as well as shorter-range datanetworks for computer systems, among many others. Generally, wirelesscommunications involve a radio frequency (RF) carrier signal that isvariously modulated to represent data, and the modulation, transmission,receipt, and demodulation of the signal conform to a set of standardsfor coordination of the same. For wireless data networks, such standardsinclude Wireless LAN (IEEE 802.11x), Bluetooth (IEEE 802.15.1), andZigBee (IEEE 802.15.4), which are understood to be time domain duplexsystems where a bi-directional link is emulated on a time-divided singlecommunications channel.

A fundamental component of any wireless communications system is thetransceiver, that is, the combined transmitter and receiver circuitry.The transceiver, with its digital baseband subsystem, encodes thedigital data to a baseband signal and modulates the baseband signal withan RF carrier signal. The modulation utilized for WLAN, Bluetooth andZigBee include orthogonal frequency division multiplexing (OFDM),quadrature phase shift keying (QPSK), and quadrature amplitudemodulation (16 QAM, 64 QAM). Upon receipt, the transceiver down-convertsthe RF signal, demodulates the baseband signal, and decodes the digitaldata represented by the baseband signal. An antenna connected to thetransceiver converts the electrical signal to electromagnetic waves, andvice versa. Depending upon its particular configuration, the transceivermay include a dedicated transmit (TX) line and a dedicated receive (RX)line, or the transceiver may have a combined transmit/receive line. Thetransmit line and the receive line are tied to a single antenna,particularly for low-cost and/or small-size applications.

RF circuitry such as the transceiver is produced as integrated circuits,typically with complementary metal-oxide semiconductor (CMOS)technology, due in part to the successes in miniaturization and costreduction efforts. Small geometry CMOS devices have reduced current drawand require lower battery voltages, thus being suitable for portableapplications that have substantial power consumption limitations.Wireless communication links must be reliable and have high datathroughput over wide distances, necessitating higher power levels at theantenna stage. For instance, the aforementioned Wireless LAN andBluetooth typically require power levels of up to and above 20 dBm.

Higher power output, in turn, requires higher current and voltage levelsin the RF circuitry. Many CMOS devices are currently produced with a0.18-micron process, with advanced systems utilizing 130 nm, 90 nm, 65nm, and 45 nm processes. The resulting integrated circuits haveoperating voltages in the range of 1.8 v to lower than 1.2 v because ofthe reduced break down voltages of the semiconductor devices therein.Although current draw is typically not an issue because of the existenceof simple solutions involving multiple active devices connected inparallel, +20 dBm power levels at 1.8 v have been difficult to achieve,particularly for signals having envelope variations, as is the case withOFDM, QPSK, QAM, and the like. Increasing current draw introducesseveral new issues including decreased efficiency because of a greaterproportion of power being lost as heat, and decreased battery life.Furthermore, the impedance is lowered for the same power level withincreased current. Considering that most RF circuits have a 50-Ohmimpedance, the design of matching circuits for decreased impedance alsobecomes an issue, typically due to increased power losses.

Conventional transceivers for WLAN, Bluetooth, ZigBee, and the liketypically do not generate sufficient power or have sufficientsensitivity necessary for reliable communications. Current integratedcircuit transceiver devices have transmit power levels of below 0 dBm,though there are some devices that have power levels of about 10 dBm,which is still significantly less than the desired 20 dBm noted above.Accordingly, additional conditioning of the RF signal is necessary.

The circuitry between the transceiver and the antenna is also referredto as the front-end module, which includes a power amplifier forincreased transmission power, and/or a low noise amplifier for increasedreception sensitivity. Various filter circuits such as band pass filtersmay also be included to provide a clean transmission signal at theantenna, and/or to protect the reception circuitry from externalblocking signals reaching the antenna. In order to rapidly switchbetween receive and transmit functions, and in order to preventinterference during the transitions between transmission and reception,the front-end module also typically includes an RF switch that iscontrolled by a general-purpose input/output line of the transceiver.The RF switch is understood to be a single-pole, double-throw switchconnecting a single antenna to either the input of the low noiseamplifier or the output of the power amplifier. Transceivers with ashared transmit and receive line such as those used in connection withBluetooth and ZigBee systems, generally include a second RF switch atthe input of the power amplifier and the output of the low noiseamplifier for the proper control of transmit and receive lines at thetransceiver end. The second RF switch is controlled by the samegeneral-purpose input/output line of the transceiver that controls thefirst RF switch. The power amplifier may also be turned on or off by anenable output from the transceiver. The enable line may have varyingvoltages to control gain or setting the power amplifier bias current.

Interrelated performance, fabrication, and cost issues have necessitatedthe fabrication of the RF switch on a different substrate than thesubstrate of the power amplifier and the low noise amplifier. Poweramplifiers are typically fabricated on a gallium arsenide (GaAs)substrate, which is understood to provide high breakdown voltages andreliability. Other substrates such as silicon germanium (SiGe) may alsobe utilized. Furthermore, the power amplifier can utilizehetero-junction bipolar transistors (HBT), metal-semiconductor fieldeffect transistors (MESFET) or high electron mobility transistors(HEMT), with the HBT being the least costly to fabricate. Along theselines, the low noise amplifier may also be fabricated on a GaAssubstrate with HBT transistors. However, because of high insertion lossor low isolation, an RF switch using HBT transistors suffers from poorperformance characteristics.

Various solutions to the forgoing issues have been proposed. Oneinvolves a multi-die configuration in which the power amplifier and thelow noise amplifier are fabricated on one die using HBT transistors, andthe RF switch is fabricated on another die using, for example, HEMTtransistors. Both of the dies are then encapsulated in a single package.The added costs associated with the GaAs substrate as compared toconventional silicon substrates, and the complex packaging processfurther elevates the cost of the front-end module fabricated inaccordance therewith. Another proposal is directed to a composite GaAssubstrate having both HBT and HEMT transistors for the power amplifierand the low noise amplifier, and the RF switch, respectively. Again,however, such integrated circuits are costly to manufacture. Yet anotherproposal is the use of a silicon substrate for the low noise amplifier,the power amplifier, and the RF switch. Because of poor isolationassociated with silicon substrates, however, higher cost solutions suchas silicon on insulator (SOI) may be used. These integrated circuitstypically require a negative voltage generator, which results in alarger die for its bias circuitry. Additionally, spurious signals over awide frequency range emitted by a charge pump for the negative voltagegenerator necessitates a physical separation thereof that furtherincreases die size.

The RF switch thus represents a significant constraint on the design oftransceiver front-ends. Accordingly, there is a need in the art for RFtransmit/receive front-end circuits without conventional RF switcheswith sufficient transmitter output and receiver sensitivity fortime-domain duplex applications.

BRIEF SUMMARY

In accordance with various embodiments of the present invention, a frontend circuit for coupling an antenna to a radio frequency (RF)transceiver is contemplated. The transceiver may include a transmitline, a receive line, a first enable line, and a second enable line. Thefront end circuit may include an antenna port, as well as a poweramplifier and a low noise amplifier. The power amplifier may include asignal output and a signal input that can be coupled to the transmitline of the transceiver. The power amplifier may also include a firstcontrol circuit that is coupled to the first enable line of thetransceiver. A first voltage that is applied to the first controlcircuit may activate and set a bias point of the power amplifier.Furthermore, the low noise amplifier may include a signal input and asignal output that is coupled to the receive line of the transceiver.The low noise amplifier may also include a second control circuit thatis coupled to the second enable line of the transceiver. A secondvoltage applied to the second control circuit may activate and set abias point of the low noise amplifier. The front end circuit may alsoinclude a matching network that is connected to the antenna port, aswell as the signal output of the power amplifier and the signal input ofthe low noise amplifier. The signal output of the power amplifier andthe signal input of the low noise amplifier may be common. The presentinvention will be best understood by reference to the following detaileddescription when read in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and advantages of the various embodimentsdisclosed herein will be better understood with respect to the followingdescription and drawings, in which:

FIG. 1A is a block diagram of an exemplary front end circuit for a radiofrequency transceiver with separate transmit and receive lines and aband pass filter in one configuration;

FIG. 1B is a block diagram of the front end circuit with the separatetransmit and receive lines and the band pass filter in anotherconfiguration;

FIG. 2A is a block diagram of another exemplary front end circuit for aradio frequency transceiver with a common transmit and receive line anda band pass filter in one configuration;

FIG. 2B is a block diagram of the front end circuit with common transmitand receive lines and a band pass filter in another configuration;

FIG. 3 is a schematic diagram of a first embodiment of the front endcircuit;

FIG. 4 is a graph illustrating 1 dB compression point over loadresistance for a variety of bias voltage utilized for determining anappropriate configuration of a matching network;

FIG. 5 is a Smith chart with constant noise figure (NF) and input returnloss (S11) circles at a fixed frequency in 50 Ohm polar coordinates;

FIGS. 6A-6D are Smith Charts of an exemplary matching of the transistorQ1;

FIG. 7A shows simulated results for a tuned matching circuit variouslyplotting the base impedance matching against the low noise amplifierinput matching;

FIG. 7B shows simulated results for the low noise amplifier basematching for constant NF;

FIG. 7C shows simulated results for the low noise amplifier basematching with constant gain circles;

FIG. 8 is a graph illustrating peak voltage over load resistance atdifferent power levels;

FIG. 9 is a graph showing peak voltages versus RF power at a poweramplifier collector;

FIG. 10 is a schematic diagram of an equivalent circuit of the matchingnetwork;

FIG. 11 is a graph of voltage swing at different power levels;

FIG. 12 is a graph of the low noise amplifier transistor base-emittervoltage at different power levels;

FIG. 13 is a schematic diagram of a second embodiment of the front endcircuit including a direct current bias switch;

FIG. 14 is a schematic diagram of a third embodiment of the front endcircuit including a cascode transistor;

FIG. 15 is a schematic diagram of a fourth embodiment of the front endcircuit with a parallel resonant circuit in a first configuration;

FIG. 16 is a graph plotting voltage reduction at the base of the lownoise amplifier of the fourth embodiment of the front end circuit;

FIG. 17 is a schematic diagram of a fifth embodiment of the front endcircuit with the parallel resonant circuit in a second configuration;

FIG. 18 is a schematic diagram of a sixth embodiment of the front endcircuit with a matching circuit voltage divider in a firstconfiguration;

FIG. 19 is a schematic diagram of a seventh embodiment of the front endcircuit with the matching circuit voltage divider in a secondconfiguration;

FIG. 20 is a schematic diagram of an eighth embodiment of the front endcircuit with another variation of the matching circuit including aseries inductor-capacitor chain;

FIG. 21 is a schematic diagram of a ninth embodiment of the front endcircuit configured for a single transmit-receive port transceiver andincluding a low noise amplifier switching transistor operating with thedirect current bias switch;

FIG. 22 is a schematic diagram of a tenth embodiment of the front endcircuit configured for the single transmit-receive port transceiver andincluding the low noise amplifier switching transistor operating withthe cascode transistor switch;

FIG. 23 is a schematic diagram of an eleventh embodiment of the frontend circuit configured for the single transmit-receive port transceiver;

FIG. 24 is a schematic diagram of a twelfth embodiment of the front endcircuit configured for the single transmit-receive port transceiver; and

FIG. 25 is a schematic diagram of a thirteenth embodiment of the frontend circuit configured for the single transmit-receive port transceiver.

Common reference numerals are used throughout the drawings and thedetailed description to indicate the same elements.

DETAILED DESCRIPTION

The detailed description set forth below in connection with the appendeddrawings is intended as a description of the presently preferredembodiment of the invention, and is not intended to represent the onlyform in which the present invention may be developed or utilized. Thedescription sets forth the functions of the invention in connection withthe illustrated embodiment. It is to be understood, however, that thesame or equivalent functions may be accomplished by differentembodiments that are also intended to be encompassed within the scope ofthe invention. It is further understood that the use of relational termssuch as first and second and the like are used solely to distinguish onefrom another entity without necessarily requiring or implying any actualsuch relationship or order between such entities.

With reference to the block diagrams of FIGS. 1A, 1B, 2A, and 2B,various embodiments contemplate a front end circuit 100 that couples anantenna 102 to a radio frequency (RF) transceiver 104. As will bedescribed in further detail below, two variants of the front end circuit100 a and 100 b are contemplated. When considering features applicableto both variants, reference will be made generally to the front endcircuit 100. The transceiver 104 generates and receives an RF signalthat is compliant with a particular communications system or standardsuch as, for example, Wireless LAN (802.11x), Bluetooth (802.15.1), orZigBee (IEEE 802.15.4). The predefined operating frequencies of thesesystems vary from 2.4 GHz to 6 GHz. It is noted that while the presentdisclosure sets forth a variety of configurations optimized for thesecommunications systems, those having ordinary skill in the art willrecognize that the front end circuit 100 may be optimized for othersystems, particularly those that utilize time domain duplexing.

The RF signal generated by the transceiver 104, which has a typicalpower level of 0 dBM, is insufficient for transmission over anything butthe shortest distances. Accordingly, the front end circuit 100 includesa power amplifier 106 to amplify the RF signal to an appropriate levelfor establishing a reliable communications link. As will be detailedbelow, various embodiments contemplate a +20 dBm power level at theantenna 102. Additionally, the transceiver 104 receives an RF signal atthe antenna 102 from a transmitting node of the communications system.In order for the transceiver 104 to properly demodulate and extract databeing carried on the very weak and noisy RF signal at the antenna 102,it is amplified by a low noise amplifier 108.

A variety of configurations of the transceiver 104 are known in the art,and front end circuits 100 specific therefor are envisioned. As bestillustrated in the block diagrams of FIGS. 1A and 1B, a first exemplaryvariant of the transceiver 104 a includes a separate transmit line 110and a receive line 112. The transceiver 104 a further includes one ormore general-purpose input/output lines 114 that are utilized to controlthe power amplifier 106 and the low noise amplifier 108, as will beconsidered in further detail below. The general-purpose input/outputlines 114 are understood to supply digital signals that are atpredefined voltages for high and low states, though some transceivers104 provide variable or analog voltages. Referring now to FIGS. 2A and2B, a second variation of the transceiver 104 b includes a commontransmit and receive line 116, in which the generated RF signals fromthe transceiver 104 and the received RF signals from the antenna 102share the connection between the transceiver 104 and the front endcircuit 100. Typically, low cost applications such as Bluetooth andZigBee are understood to utilize transceivers 104 b having thisconfiguration. The transceiver 104 b is also understood to include oneor more of the general-purpose input/output lines 114 for controllingthe power amplifier 106 and the low noise amplifier 108.

In accordance with various embodiments, the elimination of theconventional RF switch from the front end circuit 100 is generallycontemplated. Consequently, all or substantially all of the componentsof the front end circuit 100 are envisioned to be fabricated on a singledie with common transistors structures, though some embodiments are notnecessarily limited thereto, in which the components may be discretelyfabricated. Suitable transistor structures include bipolar junction(BJT), hetero-junction bipolar (HBT), metal semiconductor field effect(MESFET), metal-oxide semiconductor field effect (MOSFET), and highelectron mobility (HEMT). The single-die fabrication is understood togreatly reduce the footprint of the die for the front end circuit 100.The die may be fabricated from a silicon substrate, a gallium arsenide(GaAs) substrate, or any other suitable semiconductor material, and maybe packaged in a conventional, low-cost quad frame no lead (QFN) plasticpackage. Any other appropriate transistor structure, semiconductorsubstrate, fabrication techniques, and packaging techniques may also beutilized in accordance with various teachings in the art in light of theperformance parameters of the front end circuit 100.

As briefly noted above, time domain duplex communications systemsrequire rapidly switching between transmit and receive modes, andinstead of an RF switch, the inherent switching characteristics of thepower amplifier 106 and the low noise amplifier 108 are utilized. Thus,the front end circuit 100 in accordance with the various embodimentshave similar functional features as conventional front end modules withRF switches, with the benefit of reduced control lines. In particular,the low noise amplifier 108 and the power amplifier 106 are selectivelyactivated in a substantially exclusive relation to the other. When thetransmit line 110 is active, the power amplifier 106 is activated, whilethe low noise amplifier 108 is deactivated. The RF signal generated bythe transceiver 104 is amplified and transmitted over the antenna 102.When the receive line 112 is active, the low noise amplifier 108 isactivated, while the power amplifier 106 is deactivated. Thus, the RFsignal received through the antenna 102 is amplified and conveyed to thetransceiver 104 for further processing.

Since both the transmit chain and the receive chain share a singleconnection to the antenna 102 via the front end circuit 100, in anoptimal configuration, the amplified RF signal at the output of thepower amplifier 106 is minimized at the receive line 112, and thereceived RF signal at the input low noise amplifier 108 is non-existentat the transmit line 110. Furthermore, in relation to the secondvariation of the transceiver 104 b, because the transmit chain and thereceive chain also share a single connection to the transceiver 104 b,similar considerations are applicable. As utilized herein, the termstransmit chain and receive chain are understood to refer to theinterconnected components of the front end circuit 100 and thetransceiver 104 that relate to the transmission or broadcast, andreception, respectively, of the RF signal. Some components, such as theantenna, are understood to be part of both the transmit chain and thereceive chain, while other components such as the power amplifier 106 orthe low noise amplifier 108 are understood to be exclusive to thetransmit chain and the receive chain, respectively. Without suitableisolation between the transmit chain and the receive chain of the frontend circuit 100, particularly with high output power levels from thepower amplifier 106, leakage of the transmitted RF signal into thereceive chain may cause distortion of the same. Furthermore, a reversevoltage at the low noise amplifier 108 with a high power RF signal mayexceed reliable operation parameters, potentially leading to permanentbreakdown. Along these lines, the deactivated power amplifier 106 andthe deactivated low noise amplifier 108 is understood to exert a minimalinfluence on the remainder of the front end circuit 100.

In addition to such isolation considerations of the transmit chain andthe receive chain, the front end circuit 100, and in particular, thepower amplifier 106 and the low noise amplifier 108, have a number ofoptimal performance characteristics. These include high linear power andhigh efficiency of the power amplifier 106 without transmittingexcessive noise and spurious signals such as harmonics through theantenna 102. Additionally, the noise figure, or the amount of noiseintroduced into the RF signal by the low noise amplifier 108, isminimized, while having sufficient gain to offset any transmissionlosses and maximize sensitivity. The input mismatch loss between theantenna 102 and the low noise amplifier 108 is reduced to an acceptablelevel, nominally less than −10 dB.

Accordingly, the front end circuit 100 includes a matching network 118that is coupled to the power amplifier 106 and the low noise amplifier108. The output from the power amplifier 106 and the input to the lownoise amplifier 108 are tied together in the matching network 118 andare common. Additionally, the matching network 118 is coupled to theantenna 102. As shown in the block diagrams of FIGS. 1A, 1B, 2A, and 2B,the front end circuits 100 for either of the variations of thetransceiver 104 (separate transmit line 110 and receive line 112, orcommon transmit/receive line 116) includes the antenna-side matchingnetwork 118. Referring to FIGS. 2A and 2B specifically, the front endcircuit 100 b for the transceiver 104 b includes a second matchingnetwork 120 that couples the input of the power amplifier 106 and theoutput of the low noise amplifier 108 to the common transmit/receiveline 116. It is understood that in the front end circuit 100 a, thepower amplifier 106 and the low noise amplifier 108 are bothindependently matched to the transceiver 104 a.

The specificities regarding the configuration of the power amplifier106, the low noise amplifier 108, and the matching network 118 inrelation to the aforementioned considerations will be described ingreater detail below. It will be appreciated by those having ordinaryskill in the art that such considerations are by way of example only andnot of limitation. Furthermore, various performance trade-offs may bemade in relation to the configuration of the front end circuit 100 whilestill being within the scope of the present invention.

The quality of the transmitted RF signal can be improved, and thereceive chain can be protected from external blocking signals reachingthe antenna 102 by the addition of a band pass filter 122. As bestillustrated in FIGS. 1A and 2A, the band pass filter 122 is disposedbetween the matching network 118 and the antenna 102. In particular, theband pass filter 122 includes a first port 124 coupled to the matchingnetwork 118, and a second port 126 coupled to the antenna 102. Thisconfiguration is understood to be appropriate for power amplifiers withflexible out-of-band noise and spur containment, though transmitefficiency and receive sensitivity is reduced. In the embodiments shownin FIGS. 1B and 2B, the band pass filter 122 is disposed between thetransceiver 104 and the front end circuit 100. In relation to the firstvariation of the transceiver 104 a, as particularly illustrated in FIG.1B, the first port 124 is connected to the output of the low noiseamplifier 108, and the second port 126 is connected to the receive line112. With the second variation of the transceiver 104 shown in FIG. 2B,the first port 124 is connected to the second matching network 120, andthe second port 126 is connected to the common transmit and receive line116. This configuration is understood to have improved signaltransmission efficiency and overall receive chain sensitivity.

With reference to the circuit schematic shown in FIG. 3, a firstembodiment of the front end circuit 100 defines a transmit block 130, areceive block 132, and a shared transmit/receive block 134 thatgenerally corresponds to the matching network 118. The transmit block130 includes a TX (transmit) port 136 that is connected to the transmitline 110 from the transceiver 104, and the receive block 132 includes anRX (receive) port 138 that is connected to the receive line 112 to thetransceiver 104. Additionally, the shared transmit/receive block 134 hasan antenna port 139, over which the front end circuit 100 is coupled tothe antenna 102.

By way of example only and not of limitation, the transmit block 130 hasa single-stage power amplifier with a transistor Q1 in a common emitterconfiguration, and the receive block 132 has a single-stage low noiseamplifier with a transistor Q2 also in a common emitter configuration.It is understood that multi-stage amplifiers may also be utilized forhigher gain applications, and those having ordinary skill in the artwill recognize the appropriate modifications to the basic configurationpresented herein for such multi-stage amplifiers. In some embodiments,it is contemplated that the transistors Q1 and Q2 have a bipolarjunction structure, though in some embodiments, they may have afield-effect structure (MOSFET, MESFET, and the like). In this regard,while the present disclosure variously references bases, collectors, andemitters of bipolar junction transistors, it is to be understood thatsuch elements directly correspond to the gates, drains, and sources offield effect transistors.

As briefly noted above, the power amplifier 106 includes circuitry formatching the input of the front end circuit 100 to the 50-Ohm outputimpedance of the transceiver 104, as is common in most RF systems. Thecomponents of a power amplifier input matching network 140 includecapacitors C1 and C3, as well as inductors L1 and L2, which match thetransmit port 136 to a base 142 of the transistor Q1 while it is beingturned on and off in the predefined operating frequency range. Infurther detail, the capacitor C1 is tied to the transmit port 136, thecapacitor C3, and the inductors L1 and L2. The inductor L2 is tied tothe base 142, and the capacitor C3 is tied to ground. The poweramplifier input matching network 140 may be variously configuredaccording to different gain, linearity, and wideband operationrequirements.

Tied to the inductor L1 is an adjustable voltage source V1 that sets thebias point of the transistor Q1 of the power amplifier 106 through aresistor R1. The bias conditions, in conjunction with the size orgeometry of the transistor Q1, are chosen to maximize the operatingpower level at the antenna 102 during transmission. Additionally, an RFdecoupling capacitor C2 having a sufficiently high capacitance isconnected to the voltage source V1. These components are understood tocomprise one embodiment of a first control circuit 148 that is coupledto the general-purpose input/output line 114 of the transceiver 104. Asindicated above, a variable voltage may be generated intermittently bythe transceiver 104 on the general-purpose input/output line 114 andthus the transistor Q1, that is, the power amplifier 106 is activatedand deactivated. The first control circuit 148 is not intended to belimited to voltage supply circuits as considered above, and any othersuitable supply such as a current minor architecture may be readilysubstituted.

The transmit block 130, and specifically the collector 144 of thetransistor Q1, is connected to the shared transmit and receive block 134that generally corresponds to the matching network 118. The matchingnetwork 118 is defined by a power amplifier output matching segment 150that includes inductors L3, L4, L5 and L6, as well as capacitors C4 andC6. The power amplifier output matching segment 150 impedance matchesthe transistor Q1 to the antenna 102 at the predefined operatingfrequency when active. The collector 144 of the transistor Q1 isconnected to the inductor L3, which in turn is connected to capacitorsC4, C6, and the inductor L4. The values of the capacitor C4 and theinductor L5 connected in series thereto and to ground are selected toprovide a series resonance at the second harmonic of the predefinedoperating frequency. A voltage source V2 is connected to the inductorL4, and provides biasing to the collector 144 of the transistor Q1.Similar to the voltage source V1, an RF decoupling capacitor C5 isconnected between the voltage source V2 and ground.

The power amplifier output matching segment 150 is configured in a waythat the resistive part of the impedance at the collector 144 of thetransistor Q1 is equal or below the resistive component of an outputimpedance or transistor load impedance required for the activatedtransistor Q1 that corresponds to a predetermined 1 dB compression point(P1 dB) at a specific bias voltage. In this regard, the power amplifieroutput matching segment 150 is loaded at the antenna side by apredefined load (typically 50 Ohms) while the receive block 132,including a low noise amplifier input matching segment 152 of thematching network 118, is disconnected.

A number of parameters of the RF signal, which are particular to a givencommunications system, dictated the configuration of the matchingnetwork 118. In WLAN systems that utilize the 802.11b standard, forexample, based upon the complementary cumulative distribution function(CCDF) of various data rates ranging from 1 Mbps to 11 Mbps, it isunderstood that the maximum power level exceeds the average power levelby about 4.0 to 4.5 dB. In 802.11a and 802.11g transmissions, themaximum power level exceeds the average power level by about 7.5 to 8.0dB for data rates up to 54 Mbps. Any given data rate has a correspondingerror vector magnitude (EVM), which has an inverse relation thereto.EVM, in turn, is understood to be related to p, which quantitativelydefines the distortion of a signal relative to an ideal one. In thepresent exemplary embodiment, a peak to average power of about 7 dB isselected.

Referring to the graph of FIG. 4, assuming a 7 dB back-off for WLANsignals with sufficiently low EVM and the selected 1 dB compressionpoint (P1 dB) is 25 dBm, then 18 dBm maximum linear power may beachieved at the output of the power amplifier 106. With a 25 dBm P1 dB,an appropriate transistor load resistance is understood to be 18 Ohms orless for a bias voltage applied to the collector 144 of the Q1 less than3.3V, which is the typical bias voltage for portable applications.

As indicated above, the shared transmit and receive block 134 isconnected to the receive block 132, which includes the low noiseamplifier 108 and other associated circuitry. The transistor Q2 is thatof the low noise amplifier 108, and is also in a common-emitterconfiguration. Additionally connected to the emitter 158 of thetransistor Q2 is an optional degeneration inductor L9 that is tied toground. In some cases, the base-emitter impedance of the transistor Q2may be better matched to the antenna 102.

The matching network 118 includes the low noise amplifier input matchingsegment 152, which is comprised of a capacitor C9 and an inductor L10that are exclusive thereto. The low noise amplifier input matchingsegment 152 is combined with the inductors L3, L4, L5, and L6 andcapacitors C4 and C6, which are shared with the power amplifier outputmatching segment 150, to impedance match the low noise amplifier 108 tothe antenna 102 while active. The capacitor C9 and the inductor L10 areconnected in series to the collector of the transistor Q1 and a base 154of the transistor Q2.

A number of factors are applicable to the optimal configuration of thelow noise amplifier 108 and the low noise amplifier input matchingsegment 152. In particular, the size or geometry of the transistor Q2 isselected such that the resistive component of an input impedance of anactivated transistor Q2 is substantially similar to the resistivecomponent of an output impedance required for the activated transistorQ1 of the power amplifier 106. The values of the capacitor C9 and theinductor L10 are selected to reach a minimal noise figure (NF) betweenthe antenna 102 and the output of the low noise amplifier 108, as wellas a minimal input return loss for an activated transistor Q2 and adeactivated transistor Q1 of the power amplifier 106. A suitable NF,according to one embodiment, may be less than 3 dB. The input returnloss is understood to be measured from the antenna 102, and includes thereceive chain of the matching network 118, i.e., the shared poweramplifier output matching segment 150 and the low noise amplifier inputmatching segment 152. One embodiment contemplates an input return lossof less than −10 dB. The Smith chart of FIG. 5 shows constant NF andinput return loss (S11) circles at a fixed frequency in 50 Ohm polarcoordinates. An overlapping section 76 corresponds to appropriate NF andS11 matching to a 50 Ohm impedance value.

The capacitor C9 and the inductor L10 are selected to correspond to asubstantially minimized voltage swing at the base of the transistor Q2.As mentioned previously, when the power amplifier 106 is on, anoptimized configuration minimizes the voltage being applied to the lownoise amplifier 108 to prevent the transistor Q2 from conducting whilethe base-emitter resistance decreases, thereby degrading the transmittedRF signal.

The graph of FIG. 8 illustrates the theoretical peak voltages over agiven load resistance for a variety of power levels, that is, whichvoltage levels could be at the transistor Q2 base-emitter junction whendeactivated if full transmit power is applied to the same. For example,an 18-Ohm load resistance at 25 dBm output, the peak voltage isapproximately 3.3 Volts. The 0.7 Volt and 1.25 Volt thresholds arerepresentative of the silicon germanium hetero-junction bipolartransistor turn-on voltage and the gallium arsenide hetero-junctionbipolar transistor turn-on voltage, respectively. In further detail,FIG. 9 illustrate the peak voltages over a given RF power at thecollector 144 of the transistor Q1, where R=3 Ohm, at the predefinedoperating frequency of 2.45 Ghz.

With reference to the schematic diagram of FIG. 10, there is illustrateda simplified equivalent circuit of the power amplifier 106, the lownoise amplifier 108, and the matching network 11. In particular, it isunderstood that Rpa and Cpa represent the power amplifier outputimpedance while providing power to the antenna 102. The antenna matchingcircuit represents an impedance de-embedded from the antenna 102 to thecollector of the last stage of the power amplifier 106. Furthermore,Rlna and Clna represent a base-emitter impedance of the low noiseamplifier transistor Q2 when deactivated, at which state has a highimpedance compared to the impedance at the collector of the poweramplifier transistor Q1. Accordingly, the transistor Q2 is notinfluencing the signal. The capacitor C9 and the inductor L10 is anadditional matching network of the low noise amplifier input, along withthe antenna matching circuit that provides an appropriate impedance forsufficient NF and input return loss figures while the transistor Q2 isactivated. The Vpa voltage generated at the transistor Q1 is eventuallydelivered to the base of the transistor Q2, but if Vlna voltage exceedsthe turn on voltage of the transistor Q2, it starts conducting while thebase-emitter resistance decreases. In a forward-biased diode,capacitance is increasing due to the influence of diffusion capacitance.Accordingly, as indicated above, the signal from the power amplifiertransistor Q1 may deteriorate.

Generally, the smallest value of the capacitor C9 is understood toresult in the minimum voltage amplitude at the base-emitter junction ofthe transistor Q2 when the transistor Q1 (the power amplifier 106) is onand the transistor Q2 (the low noise amplifier 108) is off, thusincreasing its reliability. Additionally, linearity of the poweramplifier 106 is achieved at higher transmit power levels. Avoiding aresonance frequency of the low noise amplifier input matching segment152 close to the predefined operating frequency also decreases voltageswing at the base-emitter junction of the deactivated transistor Q2, soin one exemplary configuration, the resonance frequency is set to be atleast a few hundred MHz higher.

An adjustable voltage source V4 is also connected to the base 154 of thetransistor Q2 for activating and setting the bias point of the low noiseamplifier 108. As previously noted, a variable voltage may be generatedintermittently by the transceiver 104 on the general-purposeinput/output line 114 and so the low noise amplifier 108 is activatedand deactivated thereby. The voltage is provided through a resistivedivider 160 that includes a resistor R3 connected to the adjustablevoltage source V4 and a resistor R2 connected to ground and the resistorR3. The junction between the resistor R2 and the resistor R3 is tied tothe base 154 of the transistor Q2. The resistive divider 160 isconfigured to have a sufficient resistance to prevent shunting of theimpedance at the base 154 of the transistor Q2, that is, thebase-emitter resistance of the activated transistor Q2 is less than thatof the resistive divider 160. An RF decoupling capacitor C10 is alsoconnected to the voltage source V4. These components are understood tocomprise one embodiment of a second control circuit 162. As with thefirst control circuit 148, the second control circuit 162 is notintended to be limited to a voltage supply as above, and otherconfigurations such as a current minor are also suitable.

The aforementioned first control circuit 148 and the second controlcircuit 162 thus directs the functionality of the front end circuit 100to switch between a transmit mode and a receive mode. When the poweramplifier 106 is on, there is a voltage being applied to the firstcontrol circuit 148 at a predefined level to bias on the transistor Q1,and no voltage is applied to the second control circuit 162. When thelow noise amplifier 108 is on, there is a voltage being applied to thesecond control circuit 162 to bias on the transistor Q2, while novoltage is applied to the first control circuit 148. Although inconventional operation the activation of the first control circuit 148and the second control circuit 162 are exclusive, in some embodiments,the simultaneous activation of both may be appropriate for a diagnosticor calibration mode. In such mode, it is contemplated that thetransceiver 104 may be calibrated for such parameters as receiver gain,DC offset cancellation, and so forth. The mode may also be utilizedduring a manufacturing test procedure.

A voltage source V3 biases the transistor Q2, and is connected to acollector 156 of the transistor Q2 over the inductor L8. As with theother voltage sources in the front end circuit 100, an RF decouplingcapacitor C8 is connected to the voltage source V3.

The collector 156 of the transistor Q2 is also connected to a low noiseamplifier output matching network 164, which in turn is connected to thereceive port 138. The low noise amplifier output matching network 164includes inductors L7 and L8, and capacitor C7, and a variety ofconfigurations are possible depending upon the gain, noise figure,linearity, and wide-band operation requirements. The transceiver 104 isthus impedance matched to the low noise amplifier 108.

In accordance with various embodiments, a component of the matchingnetwork 118, specifically the inductor L6, has an electrostaticdischarge function. The resistive component of the inductor L6 iscontemplated to have a value less than 5 Ohm to provide a direct current(DC) pass from the antenna port 139 to ground in case a high voltage isaccidentally applied. Accordingly, the need for electronic dischargeclamp circuitry that degrades signal transmission performance, as istypical in silicon substrate-based semiconductor devices, is eliminated.

FIG. 13 is a circuit schematic of a second embodiment of the front endcircuit 100 that is generally defined by the transmit block 130, areceive block 166, and the shared transmit/receive block 134 thatcorresponds in part to the matching network 118. The transmit block 130includes the TX (transmit) port 136 that is connected to the transmitline 110 from the transceiver 104, and the receive block 166 includesthe RX (receive) port 138 that is connected to the receive line 112 tothe transceiver 104. The shared transmit/receive block 134 has anantenna port 139 for coupling the front end circuit 100 to the antenna102.

The features of the transmit block 130 are common with that of the firstembodiment of the front end circuit 100, and includes the single-stagepower amplifier 106 with the transistor Q1 in a common emitterconfiguration. It is understood that multi-stage amplifiers may also beutilized for higher gain applications.

The power amplifier 106 includes the power amplifier input matchingnetwork 140, which is understood to match the transmit port 136 to thebase 142 of the transistor Q1 while it is being turned on and off in thepredefined operating frequency range. The power amplifier input matchingnetwork 140 may be variously configured according to gain, linearity,and wideband operation requirements. The adjustable voltage source V1sets the bias point of the transistor Q1 of the power amplifier 106 anddefines the first control circuit 148 that is coupled to thegeneral-purpose input/output line 114 of the transceiver 104. A variablevoltage may be generated intermittently by the transceiver 104 on thegeneral-purpose input/output line 114 to activate and deactivate thetransistor Q1. As noted above, other suitable supply architecturesbesides the voltage supply circuit, such as a current mirror, may besubstituted.

The transmit block 130, via the collector 144 of the transistor Q1, isconnected to the shared transmit and receive block 134 that generallycorresponds to the matching network 118. The matching network 118 isdefined at least in part by the power amplifier output matching segment150, which impedance matches the transistor Q1 to the antenna 102 at thepredefined operating frequency when active. The power amplifier outputmatching segment 150 is configured such that the impedance at thecollector 144 of the transistor Q1 is equal or below the resistivecomponent of an output impedance or transistor load impedance requiredfor the activated transistor Q1 that corresponds to the P1 dB at aspecific bias voltage. The power amplifier output matching segment 150is loaded at the antenna side by a predefined load while the receiveblock 166, including the low noise amplifier input matching segment 152of the matching network 118, is disconnected.

The shared transmit and receive block 134 is also connected to thereceive block 166, which includes the low noise amplifier 108 and otherassociated circuitry. The matching network 118 includes the low noiseamplifier input matching segment 152 that is combined with the poweramplifier output matching segment 150 to impedance match the low noiseamplifier 108 to the antenna 102 when active. The various optimizationsrelating to the low noise amplifier 108 and the low noise amplifierinput matching segment 152 previously discussed are applicable to thisembodiment.

The adjustable voltage source V4, which is connected to the base 154 ofthe transistor Q2, is also connected to a direct current bias switch168. As described above, the variable voltage generated intermittentlyby the transceiver 104 on the general-purpose input/output line 114 isunderstood to activate and deactivate the transistor Q2. The presentembodiment contemplates activating and deactivating the direct currentbias switch 168 with the low noise amplifier 108 via the second controlcircuit 162 as in the illustrated embodiment, or independently.

Specifically, the voltage from the adjustable voltage source V4 isapplied to a base 170 of the transistor Q3 through a resistor R4, andthe bias supply voltage source V3 is connected to a collector 172 of thetransistor Q3. The resistor R4 is selected to have a minimal voltagedrop through the emitter-collector chain of the transistor Q3 whenturned on, as well as settling the bias point of the transistor Q2. Thisis understood to keep the linearity of the low noise amplifier 108 high,as a greater voltage may be applied to the collector 156 of thetransistor Q2. An RF decoupling capacitor C8 is also connected to thevoltage source V3. An emitter 174 of the transistor Q3 is connected tothe inductor L8, which is turn connected to the collector 156 of thetransistor Q2. Due to the bias supply voltage source V3 beingdisconnected from the low noise amplifier 108, and specifically thetransistor Q2 thereof, there is a higher degree of isolation between thereceive port 138 and the transmit port 136. Essentially, the transistorQ3 operates as a DC voltage switch.

The collector 156 of the transistor Q2 is connected to the low noiseamplifier output matching network 164, which in turn is connected to thereceive port 138. The transceiver 104 is impedance matched to the lownoise amplifier 108. The low noise amplifier output matching network 164may have a variety of different configurations depending upon the gain,noise figure, linearity, and wide-band operation requirements.

Referring to the circuit schematic of FIG. 14, a third embodiment of thefront end circuit 100 is generally defined by the transmit block 130, areceive block 176, and the shared transmit/receive block 134corresponding in part to the matching network 118. The transmit block130 includes the TX (transmit) port 136 that is connected to thetransmit line 110 from the transceiver 104, and the receive block 166includes the RX (receive) port 138 that is connected to the receive line112 to the transceiver 104. The shared transmit/receive block 134includes the antenna port 139 for coupling the front end circuit 100 tothe antenna 102.

The features of the transmit block 130 are common with that of the firstand second embodiments of the front end circuit 100 above, and includesthe single-stage power amplifier 106 with the transistor Q1 in a commonemitter configuration. It is understood that multi-stage amplifiers mayalso be utilized for higher gain applications.

The power amplifier 106 includes the power amplifier input matchingnetwork 140, which is understood to match the transmit port 136 to thebase 142 of the transistor Q1 while it is being turned on and off in thepredefined operating frequency range. The power amplifier input matchingnetwork 140 may be variously configured according to gain, linearity,and wideband operation requirements. The adjustable voltage source V1sets the bias point of the transistor Q1 of the power amplifier 106 anddefines the first control circuit 148 that is coupled to thegeneral-purpose input/output line 114 of the transceiver 104. A variablevoltage may be generated intermittently by the transceiver 104 on thegeneral-purpose input/output line 114 to activate and deactivate thetransistor Q1. As noted above, other suitable supply architecturesbesides the voltage supply circuit, such as a current mirror, may besubstituted.

The transmit block 130, via the collector 144 of the transistor Q1, isconnected to the shared transmit and receive block 134 that generallycorresponds to the matching network 118. The matching network 118 isdefined at least in part by the power amplifier output matching segment150, which impedance matches the transistor Q1 to the antenna 102 at thepredefined operating frequency when active. The power amplifier outputmatching segment 150 is configured such that the impedance at thecollector 144 of the transistor Q1 is equal or below the resistivecomponent of an output impedance or transistor load impedance requiredfor the activated transistor Q1 that corresponds to the P1 dB at aspecific bias voltage. The power amplifier output matching segment 150is loaded at the antenna side by a predefined load while the receiveblock 166, including the low noise amplifier input matching segment 152of the matching network 118, is disconnected.

The shared transmit and receive block 134 is also connected to thereceive block 176, which includes the low noise amplifier 108 and otherassociated circuitry. The matching network 118 includes the low noiseamplifier input matching segment 152 that is combined with the poweramplifier output matching segment 150 to impedance match the low noiseamplifier 108 to the antenna 102 when active. The receive block 176includes the transistor Q2, likewise in a common-emitter configuration.The various optimizations relating to the low noise amplifier 108 andthe low noise amplifier input matching segment 152 previously discussedare applicable to this embodiment.

The adjustable voltage source V4, which is connected to the base 154 ofthe transistor Q2, is also connected to the transistor Q3, which is in acascode configuration. The cascode transistor Q3 is inserted between thebias supply voltage source V3 and the transistor Q2. In further detail,the emitter 174 of the transistor Q3 is tied directly to the collector156 of the transistor Q2, and the collector 172 of the transistor Q3 isconnected to the inductor L8. The voltage source V3, in turn, isconnected to the inductor L8. As with the other embodiments, the RFdecoupling capacitor C8 is connected to the voltage source V3.Optionally, the emitter 174 of the transistor Q3 may be connected to thecollector 156 through an additional inductor to minimize the overallnoise figure.

The variable voltage generated intermittently by the transceiver 104 onthe general-purpose input/output line 114 is understood to activate anddeactivate the transistor Q2. The present embodiment further envisionsactivating and deactivating the cascode transistor Q3 synchronouslytherewith, either via the second control circuit 162 as shown orindependently.

As discussed above, the adjustable voltage source V4 activates and setsthe bias point of the transistor Q2. Additionally, in the present thirdembodiment, the adjustable voltage source V4 is connected to the base170 of the transistor Q3 through the resistor R4. The resistor R4 isselected to settle the bias point of the transistor Q2. In addition, acapacitor C11 is connected to the base 170 of the transistor Q3 andground. The value selected for the capacitor C11 is based upon thecircuit stability requirements while the low noise amplifier 108 isactivated, as well as the overall gain shape of the same.

The collector 172 of the transistor Q3 is connected to the low noiseamplifier output matching network 164, which in turn is connected to thereceive port 138. The transceiver 104 is thus impedance matched to thelow noise amplifier 108. It is understood that the cascode configurationof the low noise amplifier 108 above results in a higher gain from theantenna port 139 to the receive port 138, as well as a higher reverseisolation between the transmit port 136 and the receive port 138, andbetween the receive port 136 and the antenna port 139. The low noiseamplifier output matching network 164, along with the size or geometryof the transistor Q3, may have a variety of different configurationsdepending upon the gain, noise figure, linearity, and wide-bandoperation requirements.

As shown in the schematic diagram of FIG. 15, a fourth embodiment of thefront end circuit 100 includes a transmit block 178, the receive block176, and the shared transmit/receive block 134 that generallycorresponds to the matching network 118. The transmit block 130 includesthe TX (transmit) port 136 that is connected to the transmit line 110from the transceiver 104, and the receive block 176 includes the RX(receive) port 138 that is connected to the receive line 112 to thetransceiver 104. The shared transmit/receive block 134 includes theantenna port 139 for coupling the front end circuit 100 to the antenna102.

The features of the transmit block 178 are substantially similar to theembodiments of the front end circuit 100 previously described, andincludes the single-stage power amplifier 106 with the transistor Q1 ina common emitter configuration. However, there are a number ofvariations as will be detailed more fully below. It is understood thatmulti-stage amplifiers may also be utilized for higher gainapplications.

The power amplifier 106 includes the power amplifier input matchingnetwork 140, which is understood to match the transmit port 136 to thebase 142 of the transistor Q1 while it is being turned on and off in thepredefined operating frequency range. The power amplifier input matchingnetwork 140 may be variously configured according to gain, linearity,and wideband operation requirements. The adjustable voltage source V1sets the bias point of the transistor Q1 of the power amplifier 106 anddefines the first control circuit 148 that is coupled to thegeneral-purpose input/output line 114 of the transceiver 104. A variablevoltage may be generated intermittently by the transceiver 104 on thegeneral-purpose input/output line 114 to activate and deactivate thetransistor Q1. Other suitable supply architectures besides the voltagesupply circuit, such as a current minor, may be substituted.

The transmit block 130, via the collector 144 of the transistor Q1, isconnected to the shared transmit and receive block 134 that generallycorresponds to the matching network 118. The matching network 118 isdefined at least in part by the power amplifier output matching segment150, which impedance matches the transistor Q1 to the antenna 102 at thepredefined operating frequency when active. The power amplifier outputmatching segment 150 is configured such that the impedance at thecollector 144 of the transistor Q1 is equal or below the resistivecomponent of an output impedance or transistor load impedance requiredfor the activated transistor Q1 that corresponds to the P1 dB at aspecific bias voltage. The power amplifier output matching segment 150is loaded at the antenna side by a predefined load while the receiveblock 166, including the low noise amplifier input matching segment 152of the matching network 118, is disconnected.

The shared transmit and receive block 134 is also connected to thereceive block 176, which includes the low noise amplifier 108 and otherassociated circuitry. The receive block 176 includes the transistor Q2,likewise in a common-emitter configuration. The matching network 118includes the low noise amplifier input matching segment 152 that iscombined with the power amplifier output matching segment 150 toimpedance match the low noise amplifier 108 to the antenna 102 whenactive. The various optimizations relating to the low noise amplifier108 and the low noise amplifier input matching segment 152 previouslydiscussed are applicable to this embodiment.

The low noise amplifier 108 includes the cascode transistor Q3 that isinserted between the bias supply voltage source V3 and the transistorQ2. The second control circuit 162 is understood to synchronouslyactivate and deactivate the transistors Q2 and Q3 with the variablevoltage source V4, which is generated by the transceiver 104 on thegeneral purpose input/output line 114. The voltage source V4 isconnected to the base 154 of the transistor Q2 and the base 170 of thetransistor Q3. The collector 172 of the transistor Q3 is connected tothe low noise amplifier output matching network 164, which in turn isconnected to the receive port 138. The transceiver 104 is thus impedancematched to the low noise amplifier 108. Further details relating to thereceive block 176 having the cascode configuration are considered above.

As previously indicated, an optimal configuration of the front endcircuit reduces the voltage swing at the input of the low noiseamplifier 108 to a minimum while the power amplifier 106 is activated inorder to minimize leakage to the receive port 138 and signal distortion.The fourth embodiment of the front end circuit 100 accordinglycontemplates the addition of a parallel resonant circuit 180 insertedbetween the collector 144 of the transistor Q1 and the base 154 of thetransistor Q2. The parallel resonant circuit 180, with its low impedanceduring activation of the transistor Q3, is understood to decreasevoltage swing at the base 154 of the transistor Q2. This allows higherlinear transmit power levels, particularly where the resistive part ofthe transistor Q2 input impedance cannot be further decreased. As willbe detailed below, the parallel resonant circuit 180 is essentiallycomprised of the inductor L10 and the capacitor C14, with thecollector-emitter impedance of the activated transistor Q4 representsloss of the circuit.

In further detail, the parallel resonant circuit 180 includes atransistor Q4 with a collector 186 connected to an intermediate junction190 between the capacitor C9 and the inductor L10 of the low noiseamplifier input matching segment 152, and an emitter 188 connected tothe collector 144 of the transistor Q1 through a series capacitor C14.The value of the capacitor C14 is selected to achieve resonance betweenthe collector 144 of Q1 and the intermediate junction 190 at thepredefined operating frequency. Furthermore, the size or geometry of thetransistor Q4 is based upon the minimal resistance parameters betweenthe collector 186 and the emitter 188 while activated in the predefinedoperating frequency.

A bias supply voltage source V5 is connected to the collector 186 of thetransistor Q4 through a series resistor R6, with a RF decouplingcapacitor C12 connected to the voltage source V5 and ground.Additionally, a resistor R7 is connected between an emitter 188 of thetransistor Q4 and ground. The resistors R6 and R7 are understood tosettle the bias current of the transistor Q4, and sufficiently high toprevent influencing RF performance, that is, higher than the resistancebetween the collector 144 of the transistor Q1 and ground, as wellbetween the intermediate junction 190 and ground. Connected in serieswith the capacitor C9 and the inductor L10 is a capacitor C15 that has asufficiently large value for bias de-coupling and preventing the voltagesupply V2 to be shorted to the voltage supply V5, also referred to as adirect current blocking element. According to one embodiment, thereactive impedance of the capacitor C15 is approximately 5 to 10 timeslower than the reactive impedance of the inductor L10 at the predefinedoperating frequency. The value of the inductor L10 may also be adjustedsuch that the impedance at the collector 144 of the transistor Q1 issubstantially the same as the impedance at the base 154 of thetransistor Q2 at the predefined operating frequency.

The transistor Q4 is activated and deactivated by the first controlcircuit 148, which includes the adjustable voltage source V1 that istied to the general-purpose input/output line 114 of the transceiver104. In particular, the voltage source V1 is connected to the base 184of the transistor Q4 through a resistor R5. The resistor R5 is alsounderstood to settle the bias current of the transistor Q4 whenactivated. Independent control of the transistor Q4, however, is alsocontemplated. Accordingly, the parallel resonant circuit 180 isunderstood to be active when the power amplifier 106 is active. An RFdecoupling capacitor C13 is connected to the base of the transistor Q4,though RF performance may also be fine-tuned therewith, including theoverall gain shape of the low noise amplifier 108 when it is active.

When the transistor Q4 is off, it is understood that the equivalentresistance is greater than 1 k Ohm. Therefore, the series impedance forthe chain including capacitor C9 and the inductor L10 providessufficient Noise Figure and matching of the low noise amplifier 108 tothe antenna 102.

When the transistor Q4 is on, it is in an inverse mode, that is, thevoltage at the base 184 is higher than the voltage at the collector 186.Although other configurations contemplate the use of field effecttransistors in a normal, linear operation, several such transistors maybe connected in series to overcome the issue of the lower breakdownvoltages associated therewith. As indicated above, the inductor L10 andthe capacitor C14 chain resonates at the predefined operating frequencywith the transistor Q4 being on. In other words, a resonant resistancebetween the intermediate junction 190 and the collector 144 of thetransistor Q1 is inserted in series with the capacitor C9, effectivelybecoming a voltage divider with the voltage being applied to the base154 of the transistor Q3 being significantly reduced for the same powerlevel. Along these lines, it is understood that the lower thecollector-emitter resistance value of the activated transistor Q4 inseries with the resonating capacitor C14, the higher the resistancebetween the intermediate junction 190 and the collector 144 of thetransistor Q1. As such, a higher power level may be applied for the samevoltage and distortion level.

The graph of FIG. 16 illustrates the simulated decrease in the voltagelevel at the base 154 of the transistor Q2 for different values of thecapacitor C9 and inductor L10 chain. As will be appreciated, the voltagerejection in dB corresponds to the output power level increase.

With reference to the schematic diagram of FIG. 17, a fifth embodimentof the front end circuit 100 includes a transmit block 192, the receiveblock 176, and the shared transmit/receive block 134 that generallycorresponds to the matching network 118. The transmit block 192 includesthe TX (transmit) port 136 that is connected to the transmit line 110from the transceiver 104, and the receive block 176 includes the RX(receive) port 138 that is connected to the receive line 112 to thetransceiver 104. The shared transmit/receive block 134 includes theantenna port 139 for coupling the front end circuit 100 to the antenna102.

The features of the transmit block 192 are substantially similar to theembodiments of the front end circuit 100 previously described, andincludes the single-stage power amplifier 106 with the transistor Q1 ina common emitter configuration. However, there are a number ofvariations as will be detailed more fully below. It is understood thatmulti-stage amplifiers may also be utilized for higher gainapplications.

The power amplifier 106 includes the power amplifier input matchingnetwork 140, which is understood to match the transmit port 136 to thebase 142 of the transistor Q1 while it is being turned on and off in thepredefined operating frequency range. The power amplifier input matchingnetwork 140 may be variously configured according to gain, linearity,and wideband operation requirements. The adjustable voltage source V1sets the bias point of the transistor Q1 of the power amplifier 106 anddefines the first control circuit 148 that is coupled to thegeneral-purpose input/output line 114 of the transceiver 104. A variablevoltage may be generated intermittently by the transceiver 104 on thegeneral-purpose input/output line 114 to activate and deactivate thetransistor Q1. Other suitable supply architectures besides the voltagesupply circuit, such as a current minor, may be substituted.

The transmit block 192, via the collector 144 of the transistor Q1, isconnected to the shared transmit and receive block 176 that generallycorresponds to the matching network 118. The matching network 118 isdefined at least in part by the power amplifier output matching segment150, which impedance matches the transistor Q1 to the antenna 102 at thepredefined operating frequency when active. The power amplifier outputmatching segment 150 is configured such that the impedance at thecollector 144 of the transistor Q1 is equal or below the resistivecomponent of an output impedance or transistor load impedance requiredfor the activated transistor Q1 that corresponds to the P1 dB at aspecific bias voltage. The power amplifier output matching segment 150is loaded at the antenna side by a predefined load while the receiveblock 176, including the low noise amplifier input matching segment 152of the matching network 118, is disconnected.

The shared transmit and receive block 134 is also connected to thereceive block 176, which includes the low noise amplifier 108 and otherassociated circuitry. The receive block 176 includes the transistor Q2,likewise in a common-emitter configuration. The matching network 118includes the low noise amplifier input matching segment 152 that iscombined with the power amplifier output matching segment 150 toimpedance match the low noise amplifier 108 to the antenna 102 whenactive. The various optimizations relating to the low noise amplifier108 and the low noise amplifier input matching segment 152 previouslydiscussed are applicable to this embodiment.

The low noise amplifier 108 includes the cascode transistor Q3 that isinserted between the bias supply voltage source V3 and the transistorQ2. The second control circuit 162 is understood to synchronouslyactivate and deactivate the transistors Q2 and Q3 with the variablevoltage source V4, which is generated by the transceiver 104 on thegeneral purpose input/output line 114. The voltage source V4 isconnected to the base 154 of the transistor Q2 and the base 170 of thetransistor Q3. The collector 172 of the transistor Q3 is connected tothe low noise amplifier output matching network 164, which in turn isconnected to the receive port 138. The transceiver 104 is thus impedancematched to the low noise amplifier 108. Further details relating to thereceive block 176 having the cascode configuration are considered above.

The fifth embodiment of the front end circuit 100, like the fourthembodiment, contemplates the reduction of voltage swing at the input ofthe low noise amplifier 108 when the power amplifier 106 is on andtransmitting. In this regard, another parallel resonant circuit 194 isinserted between the collector 144 of the transistor Q1 and the base 154of the transistor Q2. The parallel resonant circuit 194, with its lowimpedance during activation of the transistor Q4, is understood todecrease voltage swing at the base 154 of the transistor Q2. This allowshigher linear transmit power levels, particularly where the resistivepart of the transistor Q2 input impedance cannot be further decreased.As will be detailed below, the parallel resonant circuit 180 isessentially comprised of the inductor L11 and the capacitor C9, with thecollector-emitter impedance of the activated transistor Q4 representsloss of the circuit.

In further detail, the parallel resonant circuit 194 includes thetransistor Q4 with the collector 186 connected over a capacitor C15 toan intermediate junction 196 between the capacitor C9 and the inductorL10 of the low noise amplifier input matching segment 152, and theemitter 188 connected to the collector 144 of the transistor Q1 throughthe series capacitor C14 and an inductor L11. The size or geometry ofthe transistor Q4 is based upon the minimal resistance parametersbetween the collector 186 and the emitter 188 while activated in thepredefined operating frequency. The capacitor C15 has a sufficientlylarge value for bias de-coupling and preventing the voltage supply V4 tobe shorted to the voltage supply V5, also referred to as a directcurrent blocking element. The reactive impedance of the capacitor C15 iscontemplated to be approximately 5 to 10 times lower than the reactiveimpedance of the inductor L11 at the predefined operating frequency. Thereactive impedance of the capacitor C14 is also contemplated to beapproximately 5 to 10 times lower than the reactive impedance of theinductor L11 at the predefined operating frequency. The capacitor C14 isunderstood to be the direct current blocking element that prevents thevoltage source V2 from shorting to ground. The value of the capacitor C9may also be adjusted such that the impedance at the collector 144 of thetransistor Q1 is substantially the same as the impedance at the base 154of the transistor Q2 at the predefined operating frequency.

The bias supply voltage source V5 is connected to the collector 186 ofthe transistor Q4 through the series resistor R6, with the RF decouplingcapacitor C12 connected to the voltage source V5 and ground.Additionally, the resistor R7 is connected between an emitter 188 of thetransistor Q4 and ground. The resistors R6 and R7 are understood tosettle the bias current of the transistor Q4, and sufficiently high toprevent influencing RF performance, that is, higher than the resistancebetween the collector 144 of the transistor Q1 and ground, as wellbetween the intermediate junction 196 and ground.

The transistor Q4 is activated and deactivated by the first controlcircuit 148, which includes the adjustable voltage source V1 that istied to the general-purpose input/output line 114 of the transceiver104. In particular, the voltage source V1 is connected to the base 184of the transistor Q4 through a resistor R5. The resistor R5 is alsounderstood to settle the bias current of the transistor Q4 whenactivated. Independent control of the transistor Q4, however, is alsocontemplated. Accordingly, the parallel resonant circuit 194 isunderstood to be active when the power amplifier 106 is active. An RFdecoupling capacitor C13 is connected to the base of the transistor Q4,though RF performance may also be fine-tuned therewith, including theoverall gain shape of the low noise amplifier 108 during receive mode.

When the transistor Q4 is off, it is understood that the equivalentresistance is greater than 1 k Ohm. Therefore, the series impedance forthe chain including capacitor C9 and the inductor L10 providessufficient Noise Figure and matching to the antenna 102.

When the transistor Q4 is on, it is in an inverse mode, that is, thevoltage at the base 184 is higher than the voltage at the collector 186.Although other configurations contemplate the use of field effecttransistors in a normal, linear operation, several such transistors maybe connected in series to overcome the issue of the lower breakdownvoltages associated therewith. The inductor L11 resonates with thecapacitor C9 at the predefined operating frequency with the transistorQ4 being on. In other words, a resonant resistance between theintermediate junction 190 and the collector 144 of the transistor Q1 isinserted in series with the inductor L10, effectively becoming a voltagedivider with the voltage being applied to the base 154 of the transistorQ3 being significantly reduced for the same power level. It is alsounderstood that the lower the collector-emitter resistance value of theactivated transistor Q4 in series with the resonating inductor L11, thehigher the resistance between the intermediate junction 190 and thecollector 144 of the transistor Q1. As such, a higher power level may beapplied for the same voltage and distortion level.

Referring to the schematic diagram of FIG. 18, a sixth embodiment of thefront end circuit 100 includes the transmit block 130, the receive block176, and a shared transmit/receive block 198 that generally correspondsto the matching network 118. The transmit block 130 includes the TX(transmit) port 136 that is connected to the transmit line 110 from thetransceiver 104, and the receive block 176 includes the RX (receive)port 138 that is connected to the receive line 112 to the transceiver104. The shared transmit/receive block 198 includes the antenna port 139for coupling the front end circuit 100 to the antenna 102.

The power amplifier 106 includes the power amplifier input matchingnetwork 140, which is understood to match the transmit port 136 to thebase 142 of the transistor Q1 while it is being turned on and off in thepredefined operating frequency range. The power amplifier input matchingnetwork 140 may be variously configured according to gain, linearity,and wideband operation requirements. The adjustable voltage source V1sets the bias point of the transistor Q1 of the power amplifier 106 anddefines the first control circuit 148 that is coupled to thegeneral-purpose input/output line 114 of the transceiver 104. A variablevoltage may be generated intermittently by the transceiver 104 on thegeneral-purpose input/output line 114 to activate and deactivate thetransistor Q1.

The transmit block 130, via the collector 144 of the transistor Q1, isconnected to the shared transmit and receive block 198 that generallycorresponds to the matching network 118. The matching network 118 isdefined at least in part by another embodiment of a power amplifieroutput matching segment 202 that includes additional components as willbe described below, which impedance matches the transistor Q1 to theantenna 102 at the predefined operating frequency when active. The poweramplifier output matching segment 202 is configured such that theimpedance at the collector 144 of the transistor Q1 is equal or belowthe resistive component of an output impedance or transistor loadimpedance required for the activated transistor Q1 that corresponds tothe P1 dB at a specific bias voltage. The power amplifier outputmatching segment 202 is loaded at the antenna side by a predefined loadwhile the receive block 166, including the low noise amplifier inputmatching segment 152 of the matching network 118, is disconnected.

The shared transmit and receive block 198 is also connected to thereceive block 176, which includes the low noise amplifier 108 and otherassociated circuitry. The receive block 176 includes the transistor Q2,likewise in a common-emitter configuration. The matching network 118includes the low noise amplifier input matching segment 152 that iscombined in part with the power amplifier output matching segment 202 toimpedance match the low noise amplifier 108 to the antenna 102 whenactive. The various optimizations relating to the low noise amplifier108 and the low noise amplifier input matching segment 152 previouslydiscussed are applicable to this embodiment.

The sixth embodiment of the front end circuit 100 contemplates anintermediate junction 200 that couples the low noise amplifier inputmatching segment 152 and the power amplifier output matching segment 202and includes a voltage divider network. This is understood to decreasevoltage swing at the base-emitter junction of the transistor Q2 when alarge signal is applied thereto. More particularly, an inductor L3-1 isconnected to the collector 144 of the transistor Q1, and an inductorL3-2 is, in turn, connected to the inductor L3-1. The point between theinductor L3-1 and the inductor L3-2 is understood to define theintermediate junction 200, to which the low noise amplifier inputmatching segment 152 is connected.

The inductor L3-2 is connected to the inductors L4, L5, and L6, andcapacitors C4 and C6, which are the parts of the power amplifier outputmatching segment 202 that, together with the low noise amplifier inputmatching segment 152, impedance match the low noise amplifier 108 to theantenna 102. In other words, the inductor L3-1 is excluded from thereceive chain. The inductor L3-1 completes the power amplifier matchingsegment 202. The inductors L3-1 and L3-2 define a voltage divider thatdelivers a lower voltage to the base 154 of the transistor Q2 when thepower amplifier 106 is activated. The values of the inductors L3-1 andL3-2 are selected to satisfy the power amplifier linearity parameters asset forth above, and the total inductance value for purposes of thepower amplifier output matching segment 202 is understood to be acombination of the two. The values of the capacitor C9 and the inductorsL10, L3-1, and L3-2 are selected to reach a minimal noise figure (NF)between the antenna 102 and the output of the low noise amplifier 108,as well as a minimal input return loss for an activated transistor Q2and a deactivated transistor Q1.

FIGS. 6A-6D are Smith charts illustrating an exemplary matching of thetransistor Q1, with each having the aforementioned NF and input returnloss circles overlaid thereon for reference. In the particular exampleof FIG. 6A, the impedance at the collector 144 of the transistor Q1 ischarted, and shows that the circuit is capacitive at the predefinedoperating frequency of 2.4 to 2.5 GHz. In this example, the inductors L1and L2 both have a zero value. Accordingly, a series inductor may beadded to bring the impedance to the overlapping section 76 where NF andinput return loss values for the low noise amplifier 108 are sufficientas noted above. Referring to FIG. 6B, the introduction of the inductorL2 having a value of 1.2 nH results in the impedance at the collector144 of the transistor Q1 falling inside the overlapping section 76,which corresponds to sufficient NF and input return loss figures. TheSmith chart of FIG. 6C illustrates an example where splitting theinductor L3 to L1 (L3-1) and L2 (L3-2), with each having equal values of06 nH, results in the impedance at the collector 144 of the transistorQ1 falling inside the overlapping section 76. With the attendantreduction in resistance at the collector 144 of the transistor Q1, ahigher power output may be possible, as well as a reduction in voltageswing. The same matching parameters from the base 142 of the transistorQ1 is charted in FIG. 6D. In further detail, the resulting matching hasthe same resistive part of as for the collector 144, though there aresome differences with respect to the reactive part.

FIG. 7A is a graph illustrating a simulated result of low noiseamplifier 108 input matching versus base matching in a dual stage poweramplifier architecture and matching circuit as configured above. Therectangular coordinates are referenced to 50 Ohms, and the appropriatematching points at the antenna port 139 are measured. The markedlocation 78 represents a matching point chosen for 1 dB compressionpoint of 24.3 dBm. Furthermore, FIG. 7B is a graph showing the simulatedresults to noise figure circles. The marked location 78 also representsthe selection of matching parameters having sufficient input return lossand noise figure values for a particular transmit performance. FIG. 7Cis a graph showing the simulated results to constant gain circles.

The graph of FIG. 11 is a simulated result showing voltages from thepower amplifier 106 in accordance with one embodiment for differentoutput power levels at 3.3V bias. Plot 86 represents the voltage at thecollector 144 of the transistor Q1, while plot 88 represents a nodebetween the inductors L1 and L2. These plots show that the voltage atthe collector 144 typically exceeds the turn-on voltage of the low noiseamplifier transistor Q2. The graph of FIG. 12, on the other hand,illustrates that when the voltage swing from the power amplifiertransistor Q1 is in the forward direction at the base-emitter diode ofthe transistor Q2, its peak level could be much less than in the reversedirection.

The low noise amplifier 108 includes the cascode transistor Q3 that isinserted between the bias supply voltage source V3 and the transistorQ2. The second control circuit 162 is understood to synchronouslyactivate and deactivate the transistors Q2 and Q3 with the variablevoltage source V4, which is generated by the transceiver 104 on thegeneral purpose input/output line 114. The voltage source V4 isconnected to the base 154 of the transistor Q2 and the base 170 of thetransistor Q3. The collector 172 of the transistor Q3 is connected tothe low noise amplifier output matching network 164, which in turn isconnected to the receive port 138. The transceiver 104 is thus impedancematched to the low noise amplifier 108. Further details relating to thereceive block 176 having the cascode configuration are considered above.

As shown in the schematic diagram of FIG. 19, a seventh embodiment ofthe front end circuit 100 includes the transmit block 130, the receiveblock 176, and a shared transmit/receive block 204 that generallycorresponds to the matching network 118. The transmit block 130 includesthe TX (transmit) port 136 that is connected to the transmit line 110from the transceiver 104, and the receive block 176 includes the RX(receive) port 138 that is connected to the receive line 112 to thetransceiver 104. The shared transmit/receive block 204 includes theantenna port 139 for coupling the front end circuit 100 to the antenna102.

The power amplifier 106 includes the power amplifier input matchingnetwork 140, which is understood to match the transmit port 136 to thebase 142 of the transistor Q1 while it is being turned on and off in thepredefined operating frequency range. The power amplifier input matchingnetwork 140 may be variously configured according to gain, linearity,and wideband operation requirements. The adjustable voltage source V1sets the bias point of the transistor Q1 of the power amplifier 106 anddefines the first control circuit 148 that is coupled to thegeneral-purpose input/output line 114 of the transceiver 104. A variablevoltage may be generated intermittently by the transceiver 104 on thegeneral-purpose input/output line 114 to activate and deactivate thetransistor Q1.

The transmit block 130, via the collector 144 of the transistor Q1, isconnected to the shared transmit and receive block 204 that generallycorresponds to the matching network 118. The matching network 118 isdefined at least in part by yet another embodiment of a power amplifieroutput matching segment 206, which impedance matches the transistor Q1to the antenna 102 at the predefined operating frequency when active.The power amplifier output matching segment 206 is configured such thatthe impedance at the collector 144 of the transistor Q1 is equal orbelow the resistive component of an output impedance or transistor loadimpedance required for the activated transistor Q1 that corresponds tothe P1 dB at a specific bias voltage. The power amplifier outputmatching segment 206 is loaded at the antenna side by a predefined loadwhile the receive block 166, including the low noise amplifier inputmatching segment 152 of the matching network 118, is disconnected.

The shared transmit and receive block 204 is also connected to thereceive block 176, which includes the low noise amplifier 108 and otherassociated circuitry. The receive block 176 includes the transistor Q2,likewise in a common-emitter configuration. The matching network 118includes the low noise amplifier input matching segment 152 that iscombined in part with the power amplifier output matching segment 202 toimpedance match the low noise amplifier 108 to the antenna 102 whenactive. The various optimizations relating to the low noise amplifier108 and the low noise amplifier input matching segment 152 previouslydiscussed are applicable to this embodiment.

The seventh embodiment of the front end circuit 100 contemplates anintermediate junction 208 that couples the low noise amplifier inputmatching segment 152 and the power amplifier output matching segment 150and includes a voltage divider network. This is understood to decreasevoltage swing at the base-emitter junction of the transistor Q2 when alarge signal is applied thereto. As an initial matter, the inductor L3is connected to the collector 144 of the transistor Q1, which in turn isconnected to the capacitors C4 and C6, as well as to an inductor L4-2.The low noise amplifier input matching segment 152 is connected to anintermediate junction 208 defined by the inductor L4-2 and an inductorL4-1. It is understood that the inductors L4-1 and L4-2 is a voltagedivider that delivers a lower RF voltage to the base 154 of thetransistor Q2.

The parts of the power amplifier output matching segment 206, includingthe inductors L4-1, L4-2, L5, and L6, and capacitors C4 and C6, inconjunction with the low noise amplifier input matching segment 152, areunderstood to impedance match the low noise amplifier 108 to the antenna102. The values of the inductors L4-1 and L4-2 are selected to satisfythe power amplifier linearity parameters as set forth above, and thetotal inductance value for purposes of the power amplifier outputmatching segment 206 is understood to be a combination of the two.Furthermore, the values of the capacitor C9 and the inductors L10, L4-1,and L4-2 are selected to reach a minimal noise figure (NF) between theantenna 102 and the output of the low noise amplifier 108, as well as aminimal input return loss for an activated transistor Q2 and adeactivated transistor Q1.

The low noise amplifier 108 includes the cascode transistor Q3 that isinserted between the bias supply voltage source V3 and the transistorQ2. The second control circuit 162 is understood to synchronouslyactivate and deactivate the transistors Q2 and Q3 with the variablevoltage source V4, which is generated by the transceiver 104 on thegeneral purpose input/output line 114. The voltage source V4 isconnected to the base 154 of the transistor Q2 and the base 170 of thetransistor Q3. The collector 172 of the transistor Q3 is connected tothe low noise amplifier output matching network 164, which in turn isconnected to the receive port 138. The transceiver 104 is thus impedancematched to the low noise amplifier 108. Further details relating to thereceive block 176 having the cascode configuration are considered above.

With reference to the schematic diagram of FIG. 20, an eighth embodimentof the front end circuit 100 includes the transmit block 130, thereceive block 176, and a shared transmit/receive block 210 thatgenerally corresponds to the matching network 118. The transmit block130 includes the TX (transmit) port 136 that is connected to thetransmit line 110 from the transceiver 104, and the receive block 176includes the RX (receive) port 138 that is connected to the receive line112 to the transceiver 104. The shared transmit/receive block 204includes the antenna port 139 for coupling the front end circuit 100 tothe antenna 102.

The features of the transmit block 130 are substantially similar to thatof the various embodiments of the front end circuit 100 described above,and includes the single-stage power amplifier 106 with the transistor Q1in a common emitter configuration. It is understood that multi-stageamplifiers may also be utilized for higher gain applications.

The power amplifier 106 includes the power amplifier input matchingnetwork 140, which is understood to match the transmit port 136 to thebase 142 of the transistor Q1 while it is being turned on and off in thepredefined operating frequency range. The power amplifier input matchingnetwork 140 may be variously configured according to gain, linearity,and wideband operation requirements. The adjustable voltage source V1sets the bias point of the transistor Q1 of the power amplifier 106 anddefines the first control circuit 148 that is coupled to thegeneral-purpose input/output line 114 of the transceiver 104. A variablevoltage may be generated intermittently by the transceiver 104 on thegeneral-purpose input/output line 114 to activate and deactivate thetransistor Q1.

The transmit block 130, via the collector 144 of the transistor Q1, isconnected to the shared transmit and receive block 210 that generallycorresponds to the matching network 118. The matching network 118 isdefined at least in part by yet another embodiment of a power amplifieroutput matching segment 212, which impedance matches the transistor Q1to the antenna 102 at the predefined operating frequency when active.The power amplifier output matching segment 212 is configured such thatthe impedance at the collector 144 of the transistor Q1 is equal orbelow the resistive component of an output impedance or transistor loadimpedance required for the activated transistor Q1 that corresponds tothe P1 dB at a specific bias voltage. The power amplifier outputmatching segment 212 is loaded at the antenna side by a predefined loadwhile the receive block 176, including the low noise amplifier inputmatching segment 152 of the matching network 118, is disconnected.

The shared transmit and receive block 210 is also connected to thereceive block 176, which includes the low noise amplifier 108 and otherassociated circuitry. More particularly, the receive block 176 includesthe transistor Q2, likewise in a common-emitter configuration. Thematching network 118 includes the low noise amplifier input matchingsegment 152 that is combined in part with the power amplifier outputmatching segment 202 to impedance match the low noise amplifier 108 tothe antenna 102 when active. The various optimizations relating to thelow noise amplifier 108 and the low noise amplifier input matchingsegment 152 previously discussed are applicable to this embodiment.

The matching network 118 is defined by a power amplifier output matchingsegment 212 that includes inductors L3, L4, L5, L6 and L9, as well ascapacitors C4 and C6. The power amplifier output matching segment 212impedance matches the transistor Q1 to the antenna 102 at the predefinedoperating frequency when active. The collector 144 of the transistor Q1is connected to the inductor L3, which in turn is connected tocapacitors C4, C6, and the inductor L4. The inductor L9 is connected inseries with the capacitor C6 to the antenna port 139. The inductor L9and the capacitor C6 are selected to have the same in-band reactiveimpedance as the other embodiments of the matching network 118. Theaddition of the inductor L9 is understood to be for the adjustment ofthe out-of-band gain shape in either transmit or receive modes.

The matching network 118 also includes the low noise amplifier inputmatching segment 152, which is comprised of the capacitor C9 and aninductor L10 that are exclusive thereto. The low noise amplifier inputmatching segment 152 is combined with the inductors L3, L4, L5, and L6and capacitors C4 and C6, which are shared with the power amplifieroutput matching segment 212, to impedance match the low noise amplifier108 to the antenna 102 while active and having a minimized noise figure.The capacitor C9 and the inductor L10 are connected in series to thecollector of the transistor Q1 and a base 154 of the transistor Q2.

The low noise amplifier 108 includes the cascode transistor Q3 that isinserted between the bias supply voltage source V3 and the transistorQ2. The second control circuit 162 is understood to synchronouslyactivate and deactivate the transistors Q2 and Q3 with the variablevoltage source V4, which is generated by the transceiver 104 on thegeneral purpose input/output line 114. The voltage source V4 isconnected to the base 154 of the transistor Q2 and the base 170 of thetransistor Q3. The collector 172 of the transistor Q3 is connected tothe low noise amplifier output matching network 164, which in turn isconnected to the receive port 138. The transceiver 104 is thus impedancematched to the low noise amplifier 108. Further details relating to thereceive block 176 having the cascode configuration are considered above.

FIG. 21 is a circuit schematic of a ninth embodiment of the front endcircuit 100 that is suitable for use in connection with the transceiver104 having a common transmit/receive line 116. This front end circuit100 is generally defined by a transmit block 214 and a receive block216, both of which share components, including a common transceiver port220 that is connectible to the common transmit/receive line 116 and anantenna port 139 for coupling the front end circuit 100 to the antenna102.

The components of the transmit block 214 are substantially similar tothat of the various embodiments of the front end circuit 100 describedabove, in particular, the second embodiment shown in FIG. 13. There is asingle-stage power amplifier 106 with the transistor Q1 in a commonemitter configuration. It is understood that multi-stage amplifiers mayalso be utilized for higher gain applications.

The power amplifier 106 includes the power amplifier input matchingnetwork 140, which is understood to match the common transceiver port220 to the base 142 of the transistor Q1 while it is being turned on andoff in the predefined operating frequency range. The power amplifierinput matching network 140 may be variously configured according togain, linearity, and wideband operation requirements. The adjustablevoltage source V1 sets the bias point of the transistor Q1 of the poweramplifier 106 and defines the first control circuit 148 that is coupledto the general-purpose input/output line 114 of the transceiver 104. Avariable voltage may be generated intermittently by the transceiver 104on the general-purpose input/output line 114 to activate and deactivatethe transistor Q1.

The transmit block 214, via the collector 144 of the transistor Q1, isconnected the matching network 118. The matching network 118 is definedat least in part by the power amplifier output matching segment 150,which impedance matches the transistor Q1 to the antenna 102 at thepredefined operating frequency when active. The power amplifier outputmatching segment 150 is configured such that the impedance at thecollector 144 of the transistor Q1 is equal or below the resistivecomponent of an output impedance or transistor load impedance requiredfor the activated transistor Q1 that corresponds to the P1 dB at aspecific bias voltage. The power amplifier output matching segment 150is loaded at the antenna side by a predefined load while the receiveblock 216, including the low noise amplifier input matching segment 152of the matching network 118, is disconnected.

The receive block 216 includes the transistor Q2, likewise in acommon-emitter configuration, and is connected to the matching network118. The matching network 118 includes the low noise amplifier inputmatching segment 152 that is combined in part with the power amplifieroutput matching segment 150 to impedance match the low noise amplifier108 to the antenna 102 when active. The various optimizations relatingto the low noise amplifier 108 and the low noise amplifier inputmatching segment 152 previously discussed are applicable to thisembodiment.

The adjustable voltage source V4, which is connected to the base 154 ofthe transistor Q2, is also connected to the direct current bias switch168. As described above, the variable voltage generated intermittentlyby the transceiver 104 on the general-purpose input/output line 114 isunderstood to activate and deactivate the transistor Q2. The presentembodiment contemplates activating and deactivating the direct currentbias switch 168 with the low noise amplifier 108 via the second controlcircuit 162 as in the illustrated embodiment, or independently.

The collector 156 of the transistor Q2 is connected to the low noiseamplifier output matching network 164. The output of the low noiseamplifier output matching network 164, in turn, is connected to a source224 of the transistor Q5, which in one exemplary embodiment is a fieldeffect transistor such as MOSFET. However, other types of transistorstructures including bipolar technology may be readily substituted. Theadjustable voltage source V4 is connected to a gate 222 of thetransistor Q5, with its drain 226 being connected to the commontransceiver port 220. As will be described more fully below, thetransistor Q5 is operating as an RF switch.

When the transistors Q2 and Q3 are turned off by the second controlcircuit 162, so is the transistor Q5. In this state, the transistor Q5is understood to have a high impedance of at least 1 k Ohm, so the poweramplifier input matching network 140 is not influenced by the low noiseamplifier 108.

When the transistor Q1 is turned off, and the low noise amplifier 108including the transistors Q2, Q3, and Q5 are activated, the base 142 ofthe transistor is understood to have a high impedance of at least 1 kOhm. Accordingly, the rest of the circuitry connected is likewise notinfluenced by the power amplifier 106. Furthermore, with the low noiseamplifier 108 activated, the low noise amplifier output matching network164 including inductors L7 and L8, the capacitor C7, and the impedanceof the open transistor Q5, as well as the power amplifier input matchingnetwork 140 including the capacitors C1 and C3 and the inductors L1 andL2 are configured to match the impedance of the common transceiver port220 at the predefined operating frequency. This impedance is typically50 Ohms. Because the output of the low noise amplifier 108 is typicallylower than required to activate the transistor Q1 of the poweramplifier, conventional matching techniques are understood to besufficient.

Referring to the circuit schematic of FIG. 22, there is contemplated atenth embodiment of the front end circuit 100, which is suitable for usein connection with the transceiver 104 having a common transmit/receiveline 116. This front end circuit 100 is generally defined by a transmitblock 215 and a receive block 217, both of which share the components ofthe other, including the common transceiver port 220 that is connectibleto the common transmit/receive line 116 and the antenna port 139 forcoupling the front end circuit 100 to the antenna 102.

The features of the transmit block 215 are substantially similar to theembodiments of the front end circuit 100 previously described, andincludes the single-stage power amplifier 106 with the transistor Q1 ina common emitter configuration. However, there are a number ofvariations as will be detailed more fully below. It is understood thatmulti-stage amplifiers may also be utilized for higher gainapplications.

The power amplifier 106 includes a power amplifier input matchingnetwork 230, which is understood to match the common transceiver port220 to the base 142 of the transistor Q1 while it is being turned on andoff in the predefined operating frequency range. More particularly, thecapacitor C1 is connected to the common transceiver port 220, and theinductor L2 is connected to the capacitor C1. Also connected to thecapacitor C1 and the inductor L2 is the capacitor C3, which in turn isconnected to the base 142 of the transistor Q1. Furthermore, theinductor L1 is connected to the base 142 of the transistor Q2, which isconnected to the adjustable voltage source V1. The adjustable voltagesource V1 sets the bias point of the transistor Q1 of the poweramplifier 106 and defines the first control circuit 148 that is coupledto the general-purpose input/output line 114 of the transceiver 104. Avariable voltage may be generated intermittently by the transceiver 104on the general-purpose input/output line 114 to activate and deactivatethe transistor Q1.

The transmit block 215, via the collector 144 of the transistor Q1, isconnected the matching network 118. The matching network 118 is definedat least in part by the power amplifier output matching segment 150,which impedance matches the transistor Q1 to the antenna 102 at thepredefined operating frequency when active. The power amplifier outputmatching segment 150 is configured such that the impedance at thecollector 144 of the transistor Q1 is equal or below the resistivecomponent of an output impedance or transistor load impedance requiredfor the activated transistor Q1 that corresponds to the P1 dB at aspecific bias voltage. The power amplifier output matching segment 150is loaded at the antenna side by a predefined load while the receiveblock 216, including the low noise amplifier input matching segment 152of the matching network 118, is disconnected.

The receive block 217 includes the transistor Q2, likewise in acommon-emitter configuration. The matching network 118 includes the lownoise amplifier input matching segment 152 that is combined in part withthe power amplifier output matching segment 150 to impedance match thelow noise amplifier 108 to the antenna 102 when active. The variousoptimizations relating to the low noise amplifier 108 and the low noiseamplifier input matching segment 152 previously discussed are applicableto this embodiment.

In further detail, the low noise amplifier 108 includes the cascodetransistor Q3 that is inserted between the bias supply voltage source V3and the transistor Q2. The second control circuit 162 is understood tosynchronously activate and deactivate the transistors Q2 and Q3 with thevariable voltage source V4, which is generated by the transceiver 104 onthe general purpose input/output line 114. The voltage source V4 isconnected to the base 154 of the transistor Q2 and the base 170 of thetransistor Q3.

The collector 172 of the transistor Q3 is connected to the low noiseamplifier output matching network 164. The output of the low noiseamplifier output matching network 164, in turn, is connected to a source224 of the transistor Q5, which in one exemplary embodiment is a fieldeffect transistor such as MOSFET. However, other types of transistorstructures including bipolar technology may be readily substituted. Theadjustable voltage source V4 is connected to a gate 222 of thetransistor Q5, with its drain 226 being connected to the commontransceiver port 220. As will be described more fully below, thetransistor Q5 is operating as an RF switch.

When the transistors Q2 and Q3 are turned off by the second controlcircuit 162, so is the transistor Q5. In this state, the transistor Q5is understood to have a high impedance of at least 1 k Ohm, so the poweramplifier input matching network 140 is not influenced by the low noiseamplifier 108.

When the transistor Q1 is turned off, and the low noise amplifier 108including the transistors Q2, Q3, and Q5 are activated, the base 142 ofthe transistor is understood to have a high impedance of at least 1 kOhm. Accordingly, the rest of the circuitry connected is likewise notinfluenced by the power amplifier 106. Furthermore, with the low noiseamplifier 108 activated, the low noise amplifier output matching network164 including inductors L7 and L8, the capacitor C7, and the impedanceof the open transistor Q5, as well as the power amplifier input matchingnetwork 140 including the capacitors C1 and C3 and the inductors L1 andL2 are configured to match the impedance of the common transceiver port220 at the predefined operating frequency. This impedance is typically50 Ohms. Because the output of the low noise amplifier 108 is typicallylower than required to activate the transistor Q1 of the poweramplifier, conventional matching techniques are understood to besufficient.

FIG. 23 is a circuit schematic of an eleventh embodiment of the frontend circuit 100 that is suitable for use in connection with thetransceiver 104 having the common transmit/receive line 116. This frontend circuit 100 is generally defined by the transmit block 214 and thereceive block 216, both of which share components of the other,including a common transceiver port 220 that is connectible to thecommon transmit/receive line 116 and an antenna port 139 for couplingthe front end circuit 100 to the antenna 102.

The components of the transmit block 214 are substantially similar tothat of the various embodiments of the front end circuit 100 describedabove, in particular, the second embodiment shown in FIG. 13. There is asingle-stage power amplifier 106 with the transistor Q1 in a commonemitter configuration. It is understood that multi-stage amplifiers mayalso be utilized for higher gain applications.

The power amplifier 106 includes the power amplifier input matchingnetwork 140, which is understood to match the common transceiver port220 to the base 142 of the transistor Q1 while it is being turned on andoff in the predefined operating frequency range. The power amplifierinput matching network 140 may be variously configured according togain, linearity, and wideband operation requirements. The adjustablevoltage source V1 sets the bias point of the transistor Q1 of the poweramplifier 106 and defines the first control circuit 148 that is coupledto the general-purpose input/output line 114 of the transceiver 104. Avariable voltage may be generated intermittently by the transceiver 104on the general-purpose input/output line 114 to activate and deactivatethe transistor Q1.

The transmit block 214, via the collector 144 of the transistor Q1, isconnected the matching network 118. The matching network 118 is definedat least in part by the power amplifier output matching segment 150,which impedance matches the transistor Q1 to the antenna 102 at thepredefined operating frequency when active. The power amplifier outputmatching segment 150 is configured such that the impedance at thecollector 144 of the transistor Q1 is equal or below the resistivecomponent of an output impedance or transistor load impedance requiredfor the activated transistor Q1 that corresponds to the P1 dB at aspecific bias voltage. The power amplifier output matching segment 150is loaded at the antenna side by a predefined load while the receiveblock 216, including the low noise amplifier input matching segment 152of the matching network 118, is disconnected.

The receive block 216 includes the transistor Q2, likewise in acommon-emitter configuration, and is connected to the matching network118. The matching network 118 includes the low noise amplifier inputmatching segment 152 that is combined in part with the power amplifieroutput matching segment 150 to impedance match the low noise amplifier108 to the antenna 102 when active. The various optimizations relatingto the low noise amplifier 108 and the low noise amplifier inputmatching segment 152 previously discussed are applicable to thisembodiment.

The adjustable voltage source V4, which is connected to the base 154 ofthe transistor Q2, is also connected to the direct current bias switch168. As described above, the variable voltage generated intermittentlyby the transceiver 104 on the general-purpose input/output line 114 isunderstood to activate and deactivate the transistor Q2. The presentembodiment contemplates activating and deactivating the direct currentbias switch 168 with the low noise amplifier 108 via the second controlcircuit 162 as in the illustrated embodiment, or independently.

The collector 156 of the transistor Q2 is connected to the low noiseamplifier output matching network 164. The output of the low noiseamplifier output matching network 164, in turn, is connected to the base142 of the transistor Q1 and the power amplifier input matching network140. When the transistors Q2 and Q3 are deactivated, the low noiseamplifier output matching network 164 is understood not to influence theimpedance at the base 142 of the transistor Q1, as such transistors havea high impedance in this state. When the transistor Q1 is deactivated,it is understood to have a high impedance of at least 1 k Ohm, so thereis minimal influence on the other parts of the circuit, in particular,the low noise amplifier 108. The low noise amplifier output matchingnetwork 164 including the inductors L7 and L8, the capacitor C7, as wellas the power amplifier input matching network 140 including thecapacitors C1 and C3 and the inductors L1 and L2 are configured to matchthe impedance of the common transceiver port 220, which is typically 50Ohms, at the predefined operating frequency. A variety of configurationswith respect to the low noise amplifier output matching network 164 arepossible depending upon the gain, noise figure, linearity, and wide-bandoperation requirements.

It is contemplated that in order to achieve high linear power at thecommon transceiver port 220 when the low noise amplifier 108 is active,the voltage swing at the base-emitter junction of the transistor Q1 isminimized. A large emitter area for the transistor Q1 is one solution,which results in low active resistance required for transmit modeoperation. The power amplifier input matching network 140 thustransforms the 50 Ohm impedance of the common transceiver port 220 to alow resistance point at the base 142 of the transistor Q1. Generally,the configuration of the low noise amplifier output matching network 164based upon synthesizing impedance transformation from the collector 156of the transistor Q2 to a pre-defined value at the base 142 of thetransistor Q1.

FIG. 24 is a circuit schematic of a twelfth embodiment of the front endcircuit 100 that is suitable for use in connection with the transceiver104 having the common transmit/receive line 116. This front end circuit100 is generally defined by a transmit block 228 and a receive block227, both of which share components of the other, including the commontransceiver port 220 that is connectible to the common transmit/receiveline 116 and the antenna port 139 for coupling the front end circuit 100to the antenna 102.

The components of the transmit block 228 are substantially similar tothat of the various embodiments of the front end circuit 100 describedabove. There is a single-stage power amplifier 106 with the transistorQ1 in a common emitter configuration. It is understood that multi-stageamplifiers may also be utilized for higher gain applications.

The power amplifier 106 includes the power amplifier input matchingnetwork 230, which is understood to match the common transceiver port220 to the base 142 of the transistor Q1 while it is being turned on andoff in the predefined operating frequency range. More particularly, thecapacitor C1 is connected to the common transceiver port 220, and theinductor L2 is connected to the capacitor C1 at a common point 232. Alsoconnected to the common point 232 is the capacitor C3, which in turn isconnected to the base 142 of the transistor Q1. Furthermore, theinductor L1 is connected to the base 142 of the transistor Q2, which isconnected to the adjustable voltage source V1. The adjustable voltagesource V1 sets the bias point of the transistor Q1 of the poweramplifier 106 and defines the first control circuit 148 that is coupledto the general-purpose input/output line 114 of the transceiver 104. Avariable voltage may be generated intermittently by the transceiver 104on the general-purpose input/output line 114 to activate and deactivatethe transistor Q1.

The transmit block 228, via the collector 144 of the transistor Q1, isconnected the matching network 118. The matching network 118 is definedat least in part by the power amplifier output matching segment 150,which impedance matches the transistor Q1 to the antenna 102 at thepredefined operating frequency when active. The power amplifier outputmatching segment 150 is configured such that the impedance at thecollector 144 of the transistor Q1 is equal or below the resistivecomponent of an output impedance or transistor load impedance requiredfor the activated transistor Q1 that corresponds to the P1 dB at aspecific bias voltage. The power amplifier output matching segment 150is loaded at the antenna side by a predefined load while the receiveblock 217, including the low noise amplifier input matching segment 152of the matching network 118, is disconnected.

The receive block 227 includes the transistor Q2, likewise in acommon-emitter configuration, and is connected to the matching network118. The matching network 118 includes the low noise amplifier inputmatching segment 152 that is combined in part with the power amplifieroutput matching segment 150 to impedance match the low noise amplifier108 to the antenna 102 when active. The various optimizations relatingto the low noise amplifier 108 and the low noise amplifier inputmatching segment 152 previously discussed are applicable to thisembodiment.

In further detail, the low noise amplifier 108 includes the cascodetransistor Q3 that is inserted between the bias supply voltage source V3and the transistor Q2. The second control circuit 162 is understood tosynchronously activate and deactivate the transistors Q2 and Q3 with thevariable voltage source V4, which is generated by the transceiver 104 onthe general purpose input/output line 114. The voltage source V4 isconnected to the base 154 of the transistor Q2 and the base 170 of thetransistor Q3.

The collector 172 of the transistor Q3 is connected to the low noiseamplifier output matching network 164. The output of the low noiseamplifier output matching network 164, in turn, is connected to commonpoint 232. When the transistors Q2 and Q3 are deactivated, the low noiseamplifier output matching network 164 is configured not to influence theimpedance at the base 142 of the transistor Q1. Although suchtransistors have high impedance when deactivated, the collector 172 ofthe transistor Q3 is not an open. When the transistor Q1 is deactivated,it is understood to have a high impedance of at least 1 k Ohm, so thereis minimal influence on the other parts of the circuit, in particular,the low noise amplifier 108.

The low noise amplifier output matching network 164 including theinductors L7 and L8, the capacitor C7, as well as the power amplifierinput matching network 140 including the capacitors C1 and C3 and theinductors L1 and L2 are configured to match the impedance of the commontransceiver port 220, which is typically 50 Ohms, at the predefinedoperating frequency. A variety of configurations with respect to the lownoise amplifier output matching network 164 are possible depending uponthe gain, noise figure, linearity, and wide-band operation requirements.

One particular embodiment envisions the inductor L1 being selected suchthat the module of its reactive impedance is approximately 5 to 10 timesthe module of the base-emitter impedance of the transistor Q1 whendeactivated and in the predefined operating frequency. The inductor L1may also be selected such that its reactive impedance is approximately 3times higher or 3 times lower than the reactive impedance of thetransistor Q1 base-emitter capacitance when the transistor Q2 isdeactivated. Further, the capacitance C3 may be selected to avoidresonance with the inductor L1 in the predefined operating frequencyrange. It is understood that a minimized value of the capacitor C3results in a capacitive voltage divider at the base 142 of thetransistor Q1 when deactivated.

Additionally, it is contemplated that the low noise amplifier outputmatching network 164, that is, the inductors L7 and L8 and the capacitorC7, overall impedance is configured to match the overall impedance ofthe series chain of the inductor L1 and the capacitor C3 in thepredefined operating frequency. In this regard, the deactivatedtransistor Q1 has a miniscule influence on the performancecharacteristics of the activated low noise amplifier 108 for high powersignals. Relatedly, the inductors L7 and L8, and the capacitor C7 mayhave values that its overall impedance is 3 to 5 times higher than anoverall impedance above the common point 232.

FIG. 25 is a circuit schematic of a thirteenth embodiment of the frontend circuit 100 that is suitable for use in connection with thetransceiver 104 having the common transmit/receive line 116. This frontend circuit 100 is generally defined by a transmit block 234 and areceive block 235, both of which share components of the other,including the common transceiver port 220 that is connectible to thecommon transmit/receive line 116 and the antenna port 139 for couplingthe front end circuit 100 to the antenna 102.

The components of the transmit block 234 are substantially similar tothat of the various embodiments of the front end circuit 100 describedabove. There is a single-stage power amplifier 106 with the transistorQ1 in a common emitter configuration. It is understood that multi-stageamplifiers may also be utilized for higher gain applications.

The power amplifier 106 includes a power amplifier input matchingnetwork 233, which is understood to match the common transceiver port2220 to the base 142 of the transistor Q1 while it is being turned onand off in the predefined operating frequency range. More particularly,the capacitor C1 is connected to the common transceiver port 220, andthe inductor L2 is connected to the capacitor C1 at a common point 232.Also connected to the common point 232 is the capacitor C3, which inturn is connected to the base 142 of the transistor Q1. Furthermore, theinductor L1 is connected to the base 142 of the transistor Q2, which isconnected to the adjustable voltage source V1. The adjustable voltagesource V1 sets the bias point of the transistor Q1 of the poweramplifier 106 and defines the first control circuit 148 that is coupledto the general-purpose input/output line 114 of the transceiver 104. Avariable voltage may be generated intermittently by the transceiver 104on the general-purpose input/output line 114 to activate and deactivatethe transistor Q1.

The transmit block 234, via the collector 144 of the transistor Q1, isconnected the matching network 118. The matching network 118 is definedat least in part by the power amplifier output matching segment 150,which impedance matches the transistor Q1 to the antenna 102 at thepredefined operating frequency when active. The power amplifier outputmatching segment 150 is configured such that the impedance at thecollector 144 of the transistor Q1 is equal or below the resistivecomponent of an output impedance or transistor load impedance requiredfor the activated transistor Q1 that corresponds to the P1 dB at aspecific bias voltage. The power amplifier output matching segment 150is loaded at the antenna side by a predefined load while the receiveblock 216, including the low noise amplifier input matching segment 152of the matching network 118, is disconnected.

The receive block 235 includes the transistor Q2, likewise in acommon-emitter configuration, and is connected to the matching network118. The matching network 118 includes the low noise amplifier inputmatching segment 152 that is combined in part with the power amplifieroutput matching segment 150 to impedance match the low noise amplifier108 to the antenna 102 when active. The various optimizations relatingto the low noise amplifier 108 and the low noise amplifier inputmatching segment 152 previously discussed are applicable to thisembodiment.

In further detail, the low noise amplifier 108 includes the cascodetransistor Q3 that is inserted between the bias supply voltage source V3and the transistor Q2. The second control circuit 162 is understood tosynchronously activate and deactivate the transistors Q2 and Q3 with thevariable voltage source V4, which is generated by the transceiver 104 onthe general purpose input/output line 114. The voltage source V4 isconnected to the base 154 of the transistor Q2 and the base 170 of thetransistor Q3.

The collector 172 of the transistor Q3 is connected to the low noiseamplifier output matching network 164. The output of the low noiseamplifier output matching network 164, in turn, is connected to commonpoint 232. When the transistors Q2 and Q3 are deactivated, the low noiseamplifier output matching network 164 is configured not to influence theimpedance at the base 142 of the transistor Q1. Although suchtransistors have high impedance when deactivated, the collector 172 ofthe transistor Q3 is not an open. When the transistor Q1 is deactivated,it is understood to have a high impedance of at least 1 k Ohm, so thereis minimal influence on the other parts of the circuit, in particular,the low noise amplifier 108.

The low noise amplifier output matching network 164 including theinductors L7 and L8, the capacitors C7 and C12, as well as the poweramplifier input matching network 140 including the capacitors C1 and C3and the inductors L1 and L2 are configured to match the impedance of thecommon transceiver port 220, which is typically 50 Ohms, at thepredefined operating frequency. A variety of configurations with respectto the low noise amplifier output matching network 164 are possibledepending upon the gain, noise figure, linearity, and wide-bandoperation requirements.

In the presently considered embodiment, the low noise amplifier outputmatching network 164 includes a capacitor C12 connected to the junctionbetween the inductor L7 and the capacitor C7, and tied to ground.Additionally, an inductor L11 is connected to the common transceiverport 220 and tied to ground. It is contemplated that these componentsare used to tune in-band or out-of-band gain shapes of the poweramplifier 106 and the low noise amplifier 108. Moreover, increasedflexibility for impedance choices at different points in the circuit isrealized. The inductor L11 is also understood to have electrostaticdischarge properties, which, as indicated above, eliminate the necessityfor ESD clamp circuits.

With further particularity, the inductor L11 is selected to obtain areactive impedance higher than 50 Ohm, and typically higher than 150 Ohmin the predefined operating frequency. The resistive part of theinductor L11 is selected with a value less than 5 Ohm to provide anadequate direct current connection to ground.

The foregoing disclosure includes a variety of different configurationsof the receive blocks, transmit blocks, and matching circuits. It willbe appreciated by those having ordinary skill in the art that suchblocks may be variously combined with others to achieve differentperformance characteristics.

The particulars shown herein are by way of example and for purposes ofillustrative discussion of the embodiments of the present invention onlyand are presented in the cause of providing what is believed to be themost useful and readily understood description of the principles andconceptual aspects of the present invention. In this regard, no attemptis made to show details of the present invention with more particularitythan is necessary for the fundamental understanding of the presentinvention, the description taken with the drawings making apparent tothose skilled in the art how the several forms of the present inventionmay be embodied in practice.

1. A radio frequency (RF) transceiver front end circuit with apredefined operating frequency for connecting a transceiver to anantenna, the front end circuit comprising: an antenna port connectibleto the antenna; a transmit port; a receive port; a power amplifierincluding a first power amplifier transistor having a base coupled tothe transmit port, a collector, and an emitter; a power amplifier inputmatching network coupling the transmit port and the base of the firstpower amplifier transistor; a power amplifier control circuit with afirst adjustable voltage source coupled to the base of the first poweramplifier transistor, the power amplifier control circuit activating andsetting a bias point of the first power amplifier transistor; a lownoise amplifier including a first low noise amplifier transistor havinga base, a collector coupled to the receive port, and an emitter; a lownoise amplifier output matching network coupling the receive port andthe collector of the first low noise amplifier transistor; a low noiseamplifier control circuit with a second adjustable voltage sourcecoupled to the base of the first low noise amplifier transistor, the lownoise amplifier control circuit activating and setting a bias point ofthe first low noise amplifier transistor; a direct current bias switchcoupled to the low noise amplifier and activated by the low noiseamplifier control circuit; and a matching circuit including a poweramplifier output matching segment coupled to the collector of the firstpower amplifier transistor and the antenna port, and a low noiseamplifier input matching segment coupled to the base of the first lownoise amplifier transistor and the antenna port, the power amplifiermatching segment having shared components with the low noise amplifiersegment.
 2. The front end circuit of claim 1, wherein the direct currentbias switch is activated together with the low noise amplifier.
 3. Thefront end circuit of claim 1, wherein the direct current bias switchincludes a switching transistor having a collector, a base coupled tothe low noise amplifier control circuit, and an emitter coupled to thecollector of the first low noise amplifier transistor via a component ofthe low noise amplifier output matching network.
 4. The front endcircuit of claim 3, further comprising: a low noise amplifier biasvoltage source coupled to the collector of the switching transistor. 5.The front end circuit of claim 3, wherein the low noise amplifier outputmatching circuit network is coupled to the collector of the first lownoise amplifier.
 6. The front end circuit of claim 3, furthercomprising: a bias settling resistor coupling the base of the switchingtransistor to the low noise amplifier control circuit.
 7. The front endcircuit of claim 1, wherein the low noise amplifier control circuitfurther includes a resistive divider having a resistance value greaterthan an activated base-emitter resistance of the first low noiseamplifier transistor.
 8. The front end circuit of claim 1, wherein thefirst transistor of the low noise amplifier has a common-emitterconfiguration.
 9. The front end circuit of claim 1, further comprising:a degeneration inductor coupled to the emitter of the first low noiseamplifier transistor and ground.
 10. The front end circuit of claim 1,wherein the power amplifier, the low noise amplifier, and the matchingnetwork are fabricated on a single die of silicon substrate.
 11. Thefront end circuit of claim 1, wherein the power amplifier, the low noiseamplifier, and the matching network are fabricated on a single die ofgallium arsenide (GaAs) substrate.
 12. The front end circuit of claim 1,wherein the power amplifier, the low noise amplifier, and the matchingnetwork are each discrete, interconnected components.